Last week I saw an amazing photo of an incredible slow cooker French dip sandwich recipe and I couldn’t stop thinking about them. I wanted those sandwiches and I wanted them bad. But then I thought, “What if I tried to make vegetarian French dip sandwiches?” and then I was on a mission. This portobello mushroom-based French dip recipe turned out really amazing on the first try. So amazing, in fact, that this is the most enthusiastic that I’ve seen my boyfriend about any recipe that I’ve made for him so far. And I feed him a lot. ;)
What is a French Dip Sandwich?
French dip sandwiches are made with tender shaved beef piled onto a French roll, topped with melted cheese (sometimes) and served with a rich broth, or au jus, for dipping. It’s absolutely delightful. BUT, because beef is so expensive these days, these vegetarian French dip sandwiches made with portobello mushrooms are a really tasty alternative. You won’t belive how delicious this broth is!
And what recipe had me drooling at my computer screen and ultimately inspired the vegetarian version? These Slow Cooker French Dip Sandwiches from Carlsbad Cravings.
How to Make a French Dip Sandwich Vegetarian
I replaced the tender beef in classic French Dip sandwiches with meaty strips of portobello mushrooms and sautéed onions to bulk them up while keeping the price low.
I’d normally add a little Worcestershire to the broth of a beef French dip, but that has anchovies in it. So, to mimic the salty-sweetness of Worcestershire, I added a little soy sauce and just a smidge of brown sugar. That hint of sweetness from the brown sugar really helped balance the flavors and made the broth complex, so don’t be tempted to skip it.
Also, I highly suggest using Better Than Bouillon to make your broth. It has a deep flavor and just the right amount of salt.
How to Store Leftovers
If you’re not eating these sandwiches all at once, store the mushroom and onions in the broth and reheat them together before piling the filling into the sandwiches and dipping them into the remaining broth. You can heat these sandwiches in a matter of minutes under the broiler, so it’s a nice quick meal for leftovers!
What Kind of Bread Should I Use?
One last note. Due to pricing and product availability, I did not use a French loaf for my sandwiches (I know, I know). Instead, I bought a pack of hoagie rolls that worked quite well. The key to choosing your bread for these sandwiches is to make sure you have something very sturdy and crusty so that it holds up to dipping in the delicious broth.
Vegetarian French Dip Sandwiches
Servings 4Ingredients
- 1 yellow onion ($0.32)
- 3 portobello mushroom caps (about ½ lb.) ($3.99)
- 2 Tbsp butter ($0.20)
- 1/8 tsp salt ($0.01)
- 1/8 tsp freshly cracked black pepper ($0.01)
- 1/4 tsp dried thyme ($0.02)
- 1/4 tsp dried oregano ($0.02)
- 2 cups vegetable broth* ($0.26)
- 1 Tbsp soy sauce ($0.06)
- 1/2 Tbsp brown sugar ($0.02)
- 1/8 tsp garlic powder ($0.01)
- 4 6-inch French or Hoagie rolls ($1.66)
- 4 slices provolone ($1.00)
Instructions
- Slice the onion into thin strips. Rinse the portobello caps to remove any dirt or debris. Slice each cap in half, then crosswise into 1/4-inch thick strips.
- Add the butter to a deep skillet along with the sliced onions. Sauté the onions over medium heat for a few minutes, or just until they begin to soften.
- Add the sliced mushrooms to the skillet along with the salt, pepper, thyme, and oregano. Sauté the mushrooms until they release all their moisture and the liquid in the bottom of the skillet has evaporated (about 10 minutes). You should see some browned bits coating the bottom of the skillet.
- Add the vegetable broth, soy sauce, brown sugar, and garlic powder and stir to dissolve the browned bits from the bottom of the skillet. Allow the liquid to come up to a simmer, then turn down to low and simmer for about 5 minutes while you toast the bread.
- Open the rolls and place them on a baking sheet, open sides up. Turn the oven on to broil and place the rolls in the oven on the middle rack. Watch the rolls closely and broil just until you see a slightly browning on the edges (about 5 minutes).
- Use a slotted spoon or tongs to take the mushrooms and onions out of the au jus. Divide the mushrooms and onions among the four rolls. Top each sandwich with a slice of provolone.
- Return the sandwiches to the oven and broil for a few minutes more, or just until the cheese is melted. Close the sandwiches up and serve with the au jus from the skillet for dipping.
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Equipment
Notes
Nutrition
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How to Make Vegetarian French Dip Sandwiches – Step by Step Photos
Slice one yellow onion into thin strips. Wash and slice three portobello caps. I used three caps, which weighed ½ lb. total. I like to slice them in half, then crosswise into strips so that the strips aren’t super long.
Add the onions and 2 Tbsp butter to a deep skillet. Sauté the onions over medium heat just until they begin to soften (about 3 minutes).
Then add the sliced mushrooms, a pinch of salt and pepper, 1/4 tsp dried oregano, and 1/4 tsp dried thyme. Sauté the mushrooms and onions until the mushrooms release all their moisture and the liquid in the bottom of the skillet evaporates. There should be some caramelized browned bits stuck to the bottom of the skillet.
Add 2 cups of vegetable broth to the skillet and stir to dissolve the browned bits off the bottom. Then add 1 Tbsp soy sauce, 1/2 Tbsp brown sugar, and 1/8 tsp garlic powder.
Let the au jus come up to a simmer, then turn it down to low and let it simmer for 5-10 minutes while you toast the bread.
Place four opened French or hoagie rolls on a baking sheet, open side up. Turn the oven on to broil and toast the bread under the broiler just until you start to see a little browning on the edges. I kept my oven rack in the middle so that the bread was far enough away from the broiler that it wouldn’t toast super fast. That gives you a little more room for error.
Use tongs or a slotted spoon to pick the mushrooms and onions up out of the au jus, then pile them onto the toasted rolls.
Add a slice of provolone to each…
Then return the sandwiches to the broiler to melt the cheese. The open bread will continue to brown here, so if your bread was a little more on the brown side after the first broil, flip the pieces over so they’ll brown on top instead.
Finally, close up the sandwiches and serve while hot! But don’t forget to ladle that yummy au jus into little bowls for dipping.
These Vegetarian French Dip Sandwiches are seriously good stuff. nomnomnom
These were awesome! I didn’t make any modifications other than subbing 2T Worcestershire for the soy/sugar mix because I’m not veggie and love the stuff to death. I also made the filling in my Instant Pot instead of on the stove (I don’t think it saved me any time, but I love the way mushrooms turn out in the IP).
I’m thinking that when my French loaf runs out I’m probably just going to put the filling & jus into a crock and broil some of the Provolone over it like a mushroom-y French Onion soup :)
Super yummy! Omitted the brown sugar.
I was surprised how much I enjoyed these! I thought they’d probably be at least alright, but I found myself excited for leftovers for lunch the next day. My husband, admittedly, was less enthusiastic than I was, but this is a guy who until the last 2 or 3 years wouldn’t even eat onion or mushroom, and he ate his entire sandwich, too. That’s actually high praise. :)
This is the best French Dip I’ve ever had. Period. I am amazed and so happy to have found it!!!
This was sooo good! Thank you! I didn’t have thyme or brown sugar so I just added alittle mable syrup & didn’t measure anything & it still tasted amazing! Pretty fool proof! Any Omni would love this too!
obsessed!! Been meaning to try these since you published. Finally got around to making it and it was a huge success! so comforting and well rounded.
Thank you so much for providing some vegetarian options for those non-meat eaters.
So excited to have this again! yuuuuuuummm
Portobello mushrooms are available in bulk in all of my local supermarkets and cost less than prepackaged ones, ranging between $3.49 and $3.95 per lb in my location. I scrape out the gills with a spoon before cooking–keeps everything from getting so black, a cosmetic thing for me. Adding the onion to this recipe adds a sweetness that is perfect with the mushrooms. I used BTB’s mushroom flavor for the broth and it was absolutely wonderful. Love this recipe!
Oh man, you’re so lucky! These were bulk mushrooms and they were about double that price. :(
This was amazing! I loved it. Will definitely make again. The only change I made was used chicken broth instead of veggie broth because that is what I had on hand (of course used the “better than bouillon!” I think the mushrooms and sauce would also taste fantastic over pasta.
Question! If I make this for a week’s worth of lunches, how should I store it? Can I make everything, then just take the sandwich with au jus on the side and warm everything up …. or should I assemble everything that morning? I love French dip in every form and I’m very excited.
I’d keep the mushrooms and au jus separate from the bread until you’re ready to eat, so that the bread doesn’t get soggy. :)
This is a winner in my house! My skeptical husband loved these and so did my 2 year old son. These are such a comforting food to eat on a cold night. Thanks for another great recipe, Beth!
Made this tonight, and it was awesome. The flavor was spot-on. I used half Provolone and half smoked Gouda for a little extra kick, but otherwise made it according to the recipe. I was really impressed at how much the broth tasted like the real deal. It was a winner both for me (a meat-eater and lover of traditional French Dip sandwiches) and my husband (a vegetarian who had never had a French Dip sandwich).
I made this for dinner last night when we had a friend over who LOVES mushrooms, and it was a huge hit! I want to put this onion/mushroom mix on everything now.
I did make a few modifications: I used beef stock instead because I had an open container in the fridge to use up, I doubled the oregano, thyme and garlic after tasting during the cooking because I wanted more of a kick, and added a dash of worchestershire because I thought it needed more salt. But even as-is before I added more spices, the flavors were great!
We served it with slices of roast beef because my husband isn’t the biggest mushroom fan and he was worried about a sandwich with nothing to distract from the mushroom texture, but even he admitted it was good enough to stand on its own without the meat.
I think you’re horrible for promoting Better than Bullion Beef – just kidding. It is amazing stuff; I’d never tried it until your recommendation and have fallen in love – so much so that a tiny bit on a spoon can occasionally satisfy a salty craving. It adds “umami” to the most unusual dishes (eggs & veggies), without overpowering the flavor of the food and I’m using it in weird and exciting ways (like I said, on a spoon to start).
Delicious!
Made these yesterday for lunch. Yummy!