Balsamic Portobello Mushroom Marinade (Grilled Portobellos)

Name: Balsamic Portobello Mushroom Marinade (Grilled Portobellos)
Prep time: 20 min
Cook time: 12 min
Total time: 32 min
Yield: 4 servings
Cuisine: Italian
Ingredients: 4 large (about 1¼ lb total) (550 g) large portobello mushroom caps, stems removed, wiped clean with a damp paper towel; ¼ cup (60 ml) balsamic vinegar; ¼ cup (60 ml) extra-virgin olive oil; 1 tbsp (15 ml) soy sauce; 3 medium cloves (9 g) garlic cloves, finely minced; 1 tbsp (3 g) fresh thyme leaves, stripped from the stems and roughly chopped; 1 tsp (5 g) Dijon mustard; 1 tsp (5 ml) maple syrup; ½ tsp (3 g) kosher salt; ¼ tsp (½ g) black pepper, freshly ground; ¼ tsp (½ g) red pepper flakes (optional); 1 tbsp (15 ml) neutral oil or olive oil, for oiling the grill grates; 2 tbsp (8 g) fresh flat-leaf parsley, finely chopped (optional)

From the MyKitchenBank Kitchen

A tangy-sweet Italian-style marinade of balsamic vinegar, olive oil, garlic and fresh thyme that turns meaty portobello caps into juicy, deeply browned grilled mushrooms. Serve as a burger swap, on polenta, or sliced over salad.

Prep: 20 min
Cook: 12 min
Wait: 35 min
Total: 1 hr 7 min
Makes: 4 grilled portobello caps (enough marinade for about 1¼ lb / 550 g mushrooms)

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Ingredients

4 servings

For the mushrooms
4 large (about 1¼ lb total) (550 g) large portobello mushroom caps, stems removed, wiped clean with a damp paper towel
For the marinade
¼ cup (60 ml) balsamic vinegar
¼ cup (60 ml) extra-virgin olive oil
1 tbsp (15 ml) soy sauce
3 medium cloves (9 g) garlic cloves, finely minced
1 tbsp (3 g) fresh thyme leaves, stripped from the stems and roughly chopped
1 tsp (5 g) Dijon mustard
1 tsp (5 ml) maple syrup
½ tsp (3 g) kosher salt
¼ tsp (0.5 g) black pepper, freshly ground
¼ tsp (0.5 g) red pepper flakes (optional)
For the grill
1 tbsp (15 ml) neutral oil or olive oil, for oiling the grill grates
To finish
2 tbsp (8 g) fresh flat-leaf parsley, finely chopped (optional)

Equipment (7)

Gas or charcoal grill (or a grill pan)
Large shallow dish or 9×13-inch (23×33 cm) baking dish
Small mixing bowl and whisk
Pastry brush
Tongs and a wide spatula
Damp paper towels or soft mushroom brush
Small spoon

Steps

Before you start

Choose large, firm portobello caps about 4–5 inches (10–12 cm) wide with dry, intact gills. Avoid slimy or shriveled ones.
Marinate for 30 minutes, no more than 2 hours. Balsamic vinegar is acidic and makes the mushrooms soft and mushy if left too long.
Start preheating the grill during the last 10 minutes of marinating so it is ready when the timer ends.
Do not rinse the mushrooms under running water. They absorb it and turn watery on the grill.

1
Clean the mushrooms
- Wipe each portobello cap all over with a damp paper towel or soft brush to remove dirt.
- Twist out and discard the stems (or save for stock).
- Do not rinse the caps under water.
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Ready when: Caps look clean and dry, with no visible dirt on the tops or in the gills.
Tip: Mushrooms are like sponges; water makes them steam instead of sear on the grill.
2
Score the caps
- With the tip of a small knife, lightly score the smooth tops of the caps in a crosshatch pattern about ⅛ inch (3 mm) deep.
- This helps the marinade soak in.
- Optionally scrape out the dark gills with a spoon for a cleaner look and less dark liquid.
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Ready when: A shallow diamond pattern is visible on each cap without cutting through.
Tip: Scoring is shallow; deep cuts will make the caps tear when flipped.
3
Whisk the marinade
- In a small bowl, whisk together the balsamic vinegar, olive oil, soy sauce, garlic, thyme, Dijon, maple syrup, salt, black pepper and the red pepper flakes if using.
- Whisk for about 30 seconds.
- Spoon 2 tablespoons (30 ml) of the marinade into a separate small bowl and set aside for basting and serving.
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Ready when: The marinade is cloudy and emulsified, with no separate pools of oil or mustard.
Tip: Reserving a portion keeps your finishing sauce clean, since the marinade the raw mushrooms sit in has been in contact with them.
4
Marinate the mushrooms
- Arrange the caps gill side up in a single layer in a shallow dish.
- Pour the larger portion of marinade over them, spooning it into the gills, and brush it over the tops.
- Turn the caps gill side down for the last 15 minutes of marinating.
- Let stand at room temperature for 30 minutes.
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Ready when: The caps look darker and glossy, and most of the marinade has been absorbed.
Tip: Do not marinate longer than 2 hours or the caps become soggy.
5
Preheat the grillOven 450°F / 230°C
- During the last 10 minutes of marinating, heat the grill to medium-high, about 425–450°F (220–230°C).
- Clean the grates with a brush, then fold a paper towel, dip it in the 1 tablespoon (15 ml) oil, and wipe it over the grates with tongs.
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Ready when: You can hold your hand 5 inches (12 cm) above the grates for only 3–4 seconds, and the grates look lightly glossy.
Tip: Oil the grates, not the mushrooms, to avoid flare-ups.
6
Grill gill side down
- Lift the caps from the dish and let the excess marinade drip off (discard the used marinade).
- Place the caps gill side down on the hot grates, close the lid, and grill for 5–6 minutes without moving them.
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Ready when: Dark grill marks have formed and the caps release easily from the grates.
Tip: If the caps stick, give them another 30–60 seconds; they release when seared.
7
Flip and finish grilling
- Flip the caps gill side up with a wide spatula.
- Brush the tops lightly with some of the reserved marinade.
- Close the lid and grill for 5–6 more minutes.
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Ready when: The caps have shrunk by about a quarter, feel tender when pierced with a knife tip, and little juices pool in the gills.
Tip: Keep the caps gill side up so the juices stay in the cap instead of dripping onto the coals.
8
Rest, slice and serve
- Move the caps to a plate and rest for 5 minutes so the juices settle.
- Slice into ½-inch (1 cm) strips or serve whole.
- Drizzle with the remaining reserved marinade and sprinkle with chopped parsley if using.
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Ready when: The caps are glossy, tender and juicy with a deep brown color.
Tip: Slice across the cap so the strips stay tender instead of stringy.

Good to know

Tips

Place the caps gill side down first for a good sear, then finish gill side up so the juices stay in.
Use a decent mid-priced balsamic vinegar; very cheap ones are harsh, and expensive aged ones are wasted on a marinade.
Pat off excess marinade before grilling to reduce flare-ups from dripping oil.
Serve on toasted ciabatta with arugula and mozzarella, over creamy polenta, or sliced on a salad.

Make ahead

"The marinade can be whisked up to 3 days ahead and kept in a sealed jar in the fridge; shake well and bring to room temperature before using. Marinated mushrooms can sit covered in the fridge for up to 2 hours before grilling."

Storage & reheating

"Room temperature: up to 2 hours. Fridge: store cooked mushrooms in an airtight container for up to 4 days. Freezer: slice and freeze for up to 2 months (texture will be softer). Reheat in a skillet over medium heat for 3–4 minutes, or on the grill for 2 minutes per side."

Substitutions

fresh thyme leaves → Dried thyme, 1 tsp (or fresh rosemary or oregano). Dried herbs are stronger, so use about one-third the amount of fresh.
soy sauce → Tamari or coconut aminos. Tamari keeps it gluten-free; coconut aminos are sweeter, so omit the maple syrup.
maple syrup → Honey or brown sugar. Use honey if not vegan; same 1 tsp amount.
large portobello mushroom caps → Large cremini mushrooms or thick eggplant slices. Cremini need only 3–4 minutes per side; eggplant slices need 4–5 minutes per side.