Vegetarian Smash Burger (With Oyster Mushrooms)

If you’ve ever felt jealous watching those ultra-crispy smash burgers get pressed into a sizzling griddle on TikTok — but you’re vegetarian — I got you. This vegetarian smash burger hits every mark. It’s juicy, savory, and crispy on the edges with a perfectly smashed oyster mushroom that mimics the meatiness of a classic patty. Add melty cheese, spicy mayo, and pickled jalapeños on a soft brioche bun? Yeah. You’re not missing out on anything.

Plus, no fake meat required. Just good mushrooms, good seasoning, and a good smash. And, if you’re looking for what else you can do with oyster mushrooms, you have to check out my classic oyster mushroom fried chicken and buffalo “chicken” burger.

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What Is a Smash Burger?

A smash burger is exactly what it sounds like: a burger that’s literally smashed onto a hot griddle or pan, creating max surface area for those crispy, lacy edges. It’s all about caramelization. Traditional ones use ground beef, but we’re flipping that narrative with smashed mushrooms that are just as satisfying (and a lot less greasy).

Let’s talk about the flavor bomb we’re building:

• Oyster Mushrooms: The MVP. When pressed and seared, they develop crispy, caramelized edges and a meaty texture that holds up beautifully on a burger.
• Dark Soy Sauce + Liquid Smoke: These two bring umami and smoky depth — like a backyard BBQ without the grill.
• Smoked Paprika, Garlic Powder, Onion Powder, Oregano: This spice blend gives layers of flavor that mimic classic burger seasoning with a hint of smokiness.
• Olive Oil: Helps create that sizzling, golden crust during the sear.
• Brioche Buns: Buttery, soft, and perfect for soaking up all the juicy goodness.
• Sriracha Mayo: A spicy, creamy kick that ties everything together. (Also: wildly addictive.)
• American Cheese: Melty and nostalgic — you can use a fancier cheese, but this gives diner-style vibes.
• Pickled Jalapeños: For a tangy, spicy pop to cut through the richness.

Expert Tips and Tricks

• Use a HOT pan: You want instant sizzle. Cast iron is best.
• Don’t crowd the pan: Give the mushrooms space to brown, not steam.
• Press with intention: Use a heavy spatula, burger press, or even a saucepan to flatten them.
• Let it sit: No moving! Let the mushrooms get that golden crust before flipping.
• Cheese trick: Add the cheese after flipping and cover the pan briefly to melt it.

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vegetarian Smash Burger

These vegetarian smash burgers are made with crispy, seared oyster mushrooms marinated in smoky seasoning, topped with melty cheese, spicy mayo, and pickled jalapeños — all on a buttery brioche bun. No fake meat. Just big flavor and bigger crunch.

prep time :15 minutes mins

cook time :8 minutes mins

Serves 1

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Ingredients

Marinade

• 2 tbsp Dark soy sauce (or reduce to 1 tbsp if you'd like. The dish can be a little salty)
• 1/2 tsp Liquid smoke
• 1/4 tsp Smoked paprika
• 1/2 tsp Garlic powder
• 1/2 tsp Onion powder
• 1 tbsp Olive oil
• 1/4 tsp Oregano
• 1/4 tsp lime juice
• 1/2 tsp maple syrup

Other

• 6 ounces Oyster mushrooms
• brioche buns
• 3 american cheese slices
• lots of pickled jalapenos

Instructions

• Make the marinade: In a bowl, mix dark soy sauce, liquid smoke, olive oil, smoked paprika, garlic powder, onion powder, and oregano.
• Marinate mushrooms: Add mushrooms to the marinade and let sit for at least 10–15 minutes while you prep everything else.
• Preheat your pan: Heat a cast iron skillet or heavy-bottomed pan over high heat Add a little oil.
• Sear and smash: Place the mushrooms gill-side down in the pan and immediately press them flat with a heavy spatula or pan. Hold for 20–30 seconds. Don’t move them. Let them sear for 2–3 minutes until golden. Repeat on other side. Keep flipping until they are perfectly seared on both sides.
• Flip and add cheese: Add your slices of American cheese on top, and cover the pan with a lid briefly to melt the cheese.
• Toast and assemble: Toast your brioche buns. Spread sriracha mayo on the bottom, add the smashed mushroom patty, pickled jalapeños, and top with the bun.

Notes

• The marinade can be a little salty! So it’s all about balancing the look with the flavor. Dark soy sauce gives this dish a beautiful rich color and umami flavor but can be a little on the salty side. You can either reduce the amount of soy sauce and/ or dilute it with about 1-2 tbsp of water. This ensures there is enough liquid to coat the entirety of your mushrooms.
• For best results, use large oyster mushroom clusters that can hold their shape.
• If you don’t have liquid smoke, try smoked paprika and a dash of Worcestershire (vegetarian).
• Want it vegan? Use vegan cheese and plant-based mayo.

Course Main Course

Cuisine American

Keyword smash burger