Portobello Mushroom Burger Recipe

Clean mushrooms

Gently wipe each portobello cap with a damp paper towel to remove dirt. Remove and discard the stems. If desired, scrape out the gills with a spoon for a milder flavor and cleaner presentation.

Make marinade

In a shallow bowl or dish large enough to hold the caps, whisk together 4 tbs olive oil, 2 tbs balsamic vinegar, 1 tbs soy sauce, 2 tsp minced garlic, 1 tsp dried oregano, 1 tsp smoked paprika, 1 tsp black pepper, and 1/2 tsp salt until combined.

Marinate mushrooms

Place mushroom caps gill-side up in the marinade, spooning some marinade into the gill area so they absorb flavor. Turn to coat both sides. Cover and refrigerate for at least 20 minutes and up to 2 hours. If short on time, marinate 10 minutes at room temperature.

Preheat a grill or grill pan over medium-high heat (about 400°F / 200°C). Brush the grill grates or pan lightly with oil. Remove mushrooms from marinade, letting excess drip off (reserve marinade). Place caps gill-side down and grill 5-6 minutes without moving to get good grill marks.

Turn caps and grill the other side 4-6 minutes more, brushing with reserved marinade during the first minute after flipping. In the last 1-2 minutes of cooking, place a slice of cheese on each cap, close grill lid or cover pan briefly to melt the cheese. Cook until mushrooms are tender but not mushy; internal temperature should be warm and juices glistening.

Prepare sauce: In a small bowl, mix 1/2 cup mayonnaise with 1 tbs Dijon mustard (and 1 tsp hot sauce if using). Taste and adjust with a pinch of salt or a squeeze of lemon if desired.

Toast buns: Spread softened butter on cut sides of 4 buns. Place cut-side down on the grill or in a skillet over medium heat until golden and crisp, about 1-2 minutes.

Assemble burgers: Spread a tablespoon of the mayo-Dijon sauce on the bottom bun. Add a handful (about 1/2 cup) of mixed greens, place the cheesy portobello cap on top, then add tomato slices (2-3 slices per burger), thin red onion slices (a few per burger), and avocado slices if using. Top with pickles if desired and the top bun smeared with remaining sauce.

Serve: Serve immediately while mushrooms are warm. Provide napkins — these are juicy and flavorful.