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. ;)
This post contains some affiliate links, which means that we make a small commission off items you purchase at no additional cost to you.
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 believe 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
Ingredients
- 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.
See how we calculate recipe costs here.
Equipment
- Enamelware Sheet Pan
Notes
Nutrition
Video
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
On regular rotation since stumbling across this recipe several years ago, a *meatless Monday* staple.
Our local grocery carries solid ciabatta sliced sandwich buns which we find sturdy and perfect for this sandwich. Buon appetito!
Delicious, filling and so flavourful. This is going into my rotation, and will be on the list to impress my vegetarian friends.
This was great, a new favorite.
These were fantastic! Definitely going into the rotation, especially with how good the au jus turned out.
How vital are the onions to this recipe? Is there something they could be replaced with, or can they be taken out without any big consequences?
That’s a tough one. To me their flavor is vital, but if you don’t like onions, missing that flavor might not be a big issue for you. The do also add to the bulk of the recipe, so you might want to add an extra portobello cap in their place.
Outstanding. I would have sworn I was eating expensive steak sandwich.
This was soooo good! My husband loved it. ย Definitely will be in my meal planning rotation.ย
FYI for future recipes- Kroger supermarkets brand Worcestershire sauce is vegan. ย ย
Nice! Thanks for the tip!
My other half is allergic to portobello mushrooms but loves all other mushrooms and has no issues with them. Is there an alternative mushroom that would work best?ย
I’m not sure, to be honest. I rarely ever use anything other than portobello and white button mushrooms, so I’m not sure how the flavors of other mushrooms might affect the outcome.
Shiitake should work basically the same. Won’t be quite as ‘meaty’ in texture, but should do well enough.
So AMAZING! Going to make this one over and over again. The only difference I made was to double up on the cheese.
These were so good!
How many days can the leftovers be stored?
I would probably keep them for 3-4 days, but it can vary depending on things like the conditions inside your refrigerator, how you have it packaged, etc.
I’m not sure if it is available in the USA, but here in the UK we have a product called Henderson’s Relish, which is almost identical in flavour profile to Worcestershire sauce, but even better! https://www.hendersonsrelish.com/
It is great for adding to anything where you want a meaty-umami flavour, whilst still being veggie and vegan-friendly.
(No, I don’t get any commission!)
I will be making these this week. But just so you know there is a vegan worcestershire sauce in stores. It looks amazing, can’t wait.
This might be the quickest I’ve become excited about a recipe in a long time. I love French dip sandwiches but haven’t eaten meat in a while. I’m definitely going to try this. Thank you!
You will NOT be dissapointed! Been making these for years and they are one of her best.