Balsamic Marinated Portobello Mushroom Burgers with Cheese
Meaty portobello mushroom caps are baked until tender and topped with melted fontina cheese to create satisfying vegetarian burgers. The earthy mushrooms pair beautifully with tangy balsamic marinade, crisp red onion, fresh lettuce, and ripe tomato slices. Served on toasted hamburger buns with Dijon mustard, these burgers offer a hearty alternative to traditional meat patties. Perfect for summer grilling or weeknight dinners when you want something substantial yet plant-forward. The recipe includes a simple potato salad side dish to round out the meal.
Ingredients
- 4 portobello mushrooms
- ½ red onion, sliced
- 3 Tbsp balsamic vinegar
- 2 Tbsp cooking oil
- 1 lemon, juice of
- 1 head small lettuce, leaves separated
- 1 large tomato, sliced
- 2 oz fontina cheese, slicedprovolone cheese1:1
Similar melting cheese with mild flavor
- 4 hamburger buns
- 1 Tbsp Dijon mustard, for serving
- ½ lb green beans, trimmed
- ½ red onion, finely chopped
- 1 Tbsp fresh dill, chopped
- 1 lb baby red potatoes, scrubbednew potatoes1:1
Similar waxy texture for potato salad
- 1 Tbsp olive oil
Instructions
- 1
Preheat oven to 425F
- 2
Line sheet pan with foil and brush with cooking oil
- 3
Place portobellos top-side down and bake until tender for 10 to 14 minutes
- 4
Top each mushroom with fontina slice and return to oven until cheese melts for 2 minutes
- 5
Toast hamburger buns while mushrooms cook
- 6
Top portobello burgers with mustard, onion slices, lettuce and tomatoes
- 7
Serve with potato salad on the side
Tips
Move grilled portobellos to indirect heat after initial searing to prevent burning while they finish cooking through
Toast buns cut-side down in a dry skillet for better texture and to prevent sogginess from burger toppings
Gently remove mushroom stems and scrape out dark gills before marinating for cleaner presentation
Good to Know
Assembled burgers best eaten immediately. Store components separately in refrigerator for up to 3 days.
Mushrooms can be baked and potato salad prepared up to 1 day ahead. Reheat mushrooms gently before serving.
Serve immediately while mushrooms are warm and cheese is melted. Provide napkins as these can be messy.
Common Mistakes
Remove mushroom gills before cooking to avoid muddy appearance
Don't overcook mushrooms to avoid rubbery texture
Substitutions
Similar waxy texture for potato salad
FAQ
Can I make these on the grill instead of the oven?
Yes, grill portobellos over high heat 2-3 minutes per side, then move to indirect heat for 6-8 minutes. Add cheese in the last minute.
What if I don't have fontina cheese?
Provolone, mozzarella, or Swiss cheese work well as substitutes. Any good melting cheese will complement the mushrooms nicely.
How long will leftover components keep?
Store cooked mushrooms, potato salad, and prepped vegetables separately in the refrigerator for up to 3 days.