Grilled Portobello Mushroom Burgers with Balsamic and Provolone

Name: Grilled Portobello Mushroom Burgers with Balsamic and Provolone
Prep time: 18 min
Cook time: 12 min
Total time: 30 min
Yield: 4 servings
Cuisine: American
Ingredients: 4 large caps (about 4 inches wide) (500 g) portobello mushroom caps, stems removed, wiped clean, gills scraped out with a spoon; 4 tbsp (60 ml) balsamic vinegar; 4 tbsp (60 ml) extra-virgin olive oil, plus a little extra for oiling the grill grates; 1 tbsp (15 ml) soy sauce; 2 cloves (8 g) garlic cloves, finely minced; 1 tsp (1 g) dried thyme; ½ tsp (3 g) kosher salt; ½ tsp (1 g) black pepper, freshly ground; ¼ cup (60 g) mayonnaise; 1 small clove (3 g) garlic clove, grated to a paste; 1 tsp (5 ml) lemon juice, fresh; 4 slices (90 g) sliced provolone cheese; 4 buns (280 g) burger buns, split; 1 cup (20 g) baby arugula; 1 large (180 g) ripe tomato, cut into 4 thick slices; 4 thin slices (40 g) red onion, sliced ¼ inch (6 mm) thick (optional)

From the MyKitchenBank Kitchen

Meaty portobello caps soak up a garlicky balsamic marinade, then char on the grill until juicy and tender. Melted provolone, peppery arugula and a quick garlic mayo make these a satisfying vegetarian burger.

Prep: 18 min
Cook: 12 min
Wait: 30 min
Total: 1 hr
Makes: 4 burgers

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Ingredients

4 servings

For the mushrooms
4 large caps (about 4 inches wide) (500 g) portobello mushroom caps, stems removed, wiped clean, gills scraped out with a spoon
4 tbsp (60 ml) balsamic vinegar
4 tbsp (60 ml) extra-virgin olive oil, plus a little extra for oiling the grill grates
1 tbsp (15 ml) soy sauce
2 cloves (8 g) garlic cloves, finely minced
1 tsp (1 g) dried thyme
½ tsp (3 g) kosher salt
½ tsp (1 g) black pepper, freshly ground
For the garlic mayo
¼ cup (60 g) mayonnaise
1 small clove (3 g) garlic clove, grated to a paste
1 tsp (5 ml) lemon juice, fresh
For assembly
4 slices (90 g) sliced provolone cheese
4 buns (280 g) burger buns, split
1 cup (20 g) baby arugula
1 large (180 g) ripe tomato, cut into 4 thick slices
4 thin slices (40 g) red onion, sliced ¼ inch (6 mm) thick (optional)

Equipment (7)

Gas or charcoal grill with grates
Large shallow dish or 9×13-inch (23×33 cm) baking dish
Small bowl and whisk
Spoon for scraping gills
Tongs and wide spatula
Pastry or basting brush
Paper towels

Steps

Before you start

Choose caps about 4 inches (10 cm) wide that are similar in size so they cook evenly.
Marinate for at least 30 minutes but no more than 1 hour, or the mushrooms turn soggy.
Do not rinse the mushrooms under water; wipe them clean with a damp paper towel so they don't absorb water.
Start heating the grill about 10 minutes before the marinating time ends, and have a spatula, tongs and brush ready.

1
Prep the mushrooms
- Twist or cut the stems off the portobello caps.
- Wipe the caps with a damp paper towel.
- Use a spoon to scrape out the dark gills from the underside; this keeps the burgers from turning muddy and gray.
- Place the caps gill-side up in a large shallow dish in a single layer.
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Ready when: Undersides look pale and smooth with no dark gills.
Tip: Don't rinse the caps; they act like sponges and will steam instead of char.
2
Make the marinade
- In a small bowl, whisk the balsamic vinegar, 4 tablespoons olive oil, soy sauce, minced garlic, thyme, salt and pepper for about 30 seconds.
- Spoon 3 tablespoons of the marinade into a second small bowl and set it aside for brushing during grilling.
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Ready when: Marinade looks cloudy and evenly blended with the garlic and herbs suspended.
Tip: Oil and vinegar separate again as they sit, so whisk the marinade again just before using.
3
Marinate the caps
- Brush the remaining marinade over the tops, edges and gill-side hollows of the caps, using it all.
- Let the caps sit at room temperature for 30 minutes, turning each cap over once at the 15-minute mark and brushing any marinade pooled in the dish back over them.
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Ready when: Caps look darker and glossy, with most of the marinade absorbed.
Tip: Do not marinate longer than 1 hour or the caps get soggy.
4
Make garlic mayo
- While the mushrooms marinate, stir together the mayonnaise, grated garlic and lemon juice in a small bowl.
- Cover and refrigerate until needed.
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Ready when: Mayo is smooth and evenly speckled with garlic.
5
Heat the grill
- About 10 minutes before the marinating ends, preheat a gas grill to medium-high, about 400°F (200°C), or build a charcoal fire and wait until the coals are covered in gray ash.
- Scrub the grates clean.
- Fold a paper towel, dip it in a little olive oil while holding it with tongs, and wipe the grates.
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Ready when: You can hold your hand 5 inches above the grates for only 3–4 seconds.
Tip: Oiled hot grates prevent sticking.
6
Grill gill-side down
- Lift the caps from the dish and blot the tops and hollows lightly with a paper towel so little oil drips onto the flames.
- Discard the marinade left in the dish.
- Place the caps gill-side down on the grill, close the lid, and cook 5 minutes without moving them.
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Ready when: Grill marks are visible and the edges look slightly shrunken.
Tip: If flare-ups occur, move the caps to a cooler spot briefly.
7
Flip and finish
- Flip the caps with a wide spatula so the hollows face up.
- Brush the tops and hollows with the 3 tablespoons of reserved fresh marinade.
- Close the lid and cook 4–5 more minutes, so the marinade cooks onto the caps.
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Ready when: A paring knife slides into the thickest part with no resistance, the caps are deeply browned and juices pool in the hollows.
Tip: Keep the reserved marinade separate from the raw mushrooms' dish so it stays clean for brushing.
8
Melt the cheese
- Place one slice of provolone in the hollow of each cap.
- Close the lid and cook 1–2 minutes.
- In the last minute, place the buns cut-side down on the cooler part of the grill to toast.
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Ready when: Cheese is fully melted and sagging over the edges; buns are golden with light grill marks.
Tip: Watch the buns closely; they scorch in seconds.
9
Assemble the burgers
- Spread garlic mayo on both halves of each bun.
- Layer the bottom bun with arugula, a tomato slice and an onion slice if using.
- With a wide spatula, set a cheesy mushroom cap on top, cheese-side up so the melted cheese stays in the hollow, then cover with the top bun.
- Serve right away.
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Ready when: Burgers stack neatly with cheese melted over the mushroom.
Tip: Slide the spatula fully under each cap so the cheese doesn't slip off.

Good to know

Tips

Scraping the gills prevents dark liquid from staining the buns and gives a cleaner flavor.
Choose caps with intact, slightly curled edges; they hold marinade and cheese better.
No grill? Cook in a hot cast-iron grill pan, or under the broiler 5 minutes per side, then add the cheese for the last 1–2 minutes.
Blot the marinated caps before grilling; less dripping oil means fewer flare-ups and better grill marks.

Make ahead

Marinate the mushrooms up to 1 hour ahead at room temperature. The garlic mayo can be made up to 3 days ahead and kept refrigerated. Grilled caps (without cheese) can be cooked up to 1 day ahead and reheated.

Storage & reheating

Best eaten immediately. Store cooked, unassembled mushroom caps in an airtight container in the fridge for up to 3 days. Reheat in a 350°F (175°C) oven for 8–10 minutes or in a skillet over medium heat for 3–4 minutes per side. Freezing is not recommended because the mushrooms turn watery when thawed. Do not leave at room temperature for more than 2 hours.

Substitutions

sliced provolone cheese → Swiss, fontina or mozzarella slices. All melt well; use vegan cheese slices for a dairy-free burger.
mayonnaise → vegan mayonnaise or Greek yogurt. Keeps the same creamy texture; use vegan mayo to make the burger fully vegan with vegan cheese.
soy sauce → tamari. Makes the burgers gluten-free if you also use gluten-free buns.
baby arugula → baby spinach or romaine. Milder flavor and slightly less peppery.