This is a deep-fried portobello mushroom patty stuffed with Muenster and sharp cheddar, breaded in panko, and served on a toasted potato roll with burger sauce, lettuce, and tomato — a close copy of Shake Shack’s ‘Shroom Burger. It takes more steps than a standard veggie burger, but the payoff is a genuinely crispy, cheese-filled patty that holds its own next to anything on a grill. Make a batch of the stuffed, breaded mushrooms ahead of time and burger night becomes fast all week.
About the ingredients
- Portobello caps: Buy caps that are similar in size — you’re sandwiching two together, so mismatched sizes mean cheese leaks out the sides during frying.
- Muenster cheese: Found near the deli slices at most grocery stores. It melts smoother than mozzarella and doesn’t turn greasy. Don’t swap it for provolone — the melt isn’t the same.
- Panko breadcrumbs: Regular breadcrumbs will work in a pinch, but panko gives you a noticeably crunchier crust that holds up longer after frying.
- Pickling brine for the sauce: Use the liquid straight from a jar of dill pickles. No need to buy anything special.
- Potato rolls: Martin’s is the standard. If you can’t find them, a brioche bun is the closest substitute in terms of softness and slight sweetness.
Before you start
The step that matters most is freezing the stuffed mushroom bundles before you bread and fry them. Fifteen to twenty minutes in the freezer firms up the cheese so it doesn’t immediately melt out when it hits hot oil — skip this and you’ll lose most of the filling before the crust sets. The second thing worth getting right is your oil temperature: keep it steady at 350°F. Too low and the breading absorbs oil and goes soggy; too high and the outside browns before the mushroom softens through. A clip-on thermometer takes the guesswork out entirely, and it’s worth using one here.
If something goes sideways
- Cheese leaked out during frying: The bundles weren’t cold enough before going in, or the edges weren’t pressed together firmly. Next time, press the caps tightly and freeze for the full time before breading.
- Breading fell off in the oil: The mushroom surface was wet. Pat the caps completely dry before you start the flour-egg-panko sequence, and let the breaded bundles rest for five minutes before frying so the coating adheres.
- Crust is pale and greasy: Oil temperature dropped, usually from adding too many patties at once. Fry one or two at a time and let the oil come back to 350°F between batches.
- Mushroom is rubbery inside: Portobellos need enough time in the oil to cook through — roughly three to four minutes per side. If the crust is browning too fast, your oil is too hot.
- Sauce is too thin: Add mayonnaise a teaspoon at a time until it reaches a consistency that won’t drip off the bun. Thin sauce slides right out on the first bite.
Keeping and reheating
Fully cooked patties keep in the fridge for up to three days in an airtight container. To reheat without losing the crust, use an air fryer at 375°F for four to five minutes — a microwave will make the breading soft and the cheese rubbery. For meal prep, the best approach is to freeze the stuffed, breaded (but unfried) bundles on a sheet pan until solid, then transfer to a zip-lock bag; they keep frozen for up to six weeks. Fry straight from frozen, adding about two extra minutes to the cook time. The burger sauce keeps refrigerated for up to a week in a sealed jar.
Shake Shack-Style ‘Shroom Burger
Ingredients
For the Portobello Mushroom Cheese Patties:
- 4 whole large portobello mushroom caps stems removed, cleaned and gills scraped
- 2 oz Muenster cheese shredded or sliced
- 2 oz cheddar cheese sharp, shredded or sliced
- 1 cup all-purpose flour
- 3 large eggs beaten
- 1 ½ cups panko breadcrumbs preferably Japanese-style for extra crispiness
- ½ tsp kosher salt
- ¼ tsp black pepper freshly ground
- 4 cups vegetable oil for deep frying
For the Burger Assembly:
- 4 pieces soft potato rolls preferably Martin’s Potato Rolls, lightly toasted
- 4 tbsp Shake Shack-style burger sauce see Chef’s Tips
- 4 leaves green leaf lettuce washed and dried
- 1 medium ripe tomato sliced into 4 thick slices
Instructions
- Prepare the Portobello Mushrooms: Clean the mushrooms by gently wiping with a damp towel and removing stems. Scrape out the gills using a spoon to create space for the cheese filling. Pat dry with paper towels and set aside.
- Fill and Freeze: Stuff each mushroom cap with a combination of Muenster and cheddar cheese. Press another mushroom cap on top, sandwich-style. Wrap each pair tightly in plastic wrap and freeze for 20 minutes. This helps the cheese stay inside during frying.
- Bread the Mushrooms: Set up a dredging station with flour in one bowl, eggs in another, and panko mixed with salt and pepper in a third. Dip each mushroom ‘burger’ in flour, then egg, then coat thoroughly in panko. Press gently to adhere.
- Fry Until Golden: In a large heavy-bottomed pot, heat vegetable oil to 350°F (175°C). Carefully lower each mushroom patty into the oil and fry for 3–4 minutes per side or until deeply golden brown and crisp. Remove with a slotted spoon and drain on a wire rack over paper towels.
- Assemble the Burgers: Toast potato rolls on a dry skillet until golden. On each bottom bun, spread 1 tbsp of burger sauce, place a lettuce leaf, a tomato slice, followed by the hot fried ‘Shroom patty. Top with the other half of the bun and press lightly.
Notes
- For the Burger Sauce: Mix 1/2 cup mayonnaise, 1 tbsp ketchup, 1 tsp Dijon mustard, 1 tsp pickle brine, 1/4 tsp paprika, and a pinch of garlic powder.
- You can add a slice of American cheese on top of the patty if desired for a double cheese effect.
- For gluten-free adaptation, use almond flour and gluten-free panko. Potato rolls can be swapped with GF burger buns.
Nutrition
FAQ
Can I bake these instead of deep-frying?
You can, but the crust won’t be as crispy and the cheese is more likely to leak. If you go that route, bake at 425°F on a wire rack set over a sheet pan for about 20 minutes, and spray the breaded patties generously with cooking oil before they go in.
How do I keep the two mushroom caps from separating while frying?
Press them together firmly after stuffing and secure the seam with two or three toothpicks before freezing. Remove the toothpicks just before you start the breading process — by that point the cheese is firm enough to hold the caps together.
Can I make the breaded patties ahead and refrigerate them overnight before frying?
Yes, and it actually works well. Place the breaded bundles on a parchment-lined tray, cover loosely with plastic wrap, and refrigerate for up to 24 hours. The coating has time to dry out slightly, which helps it stay on during frying.
More burger recipes to try
- Five Guys Veggie Sandwich Style
- Veggie Whopper Copycat Recipe
- Mushroom Swiss King Copycat
- Halloumi King Burger Homage