There is something deeply satisfying about a perfectly grilled Portobello mushroom—its meaty texture, smoky char, and earthy richness make it a star on any plate. This recipe elevates the humble fungus into a showstopping main course or a luxurious side by pairing it with a bold, peppery arugula pesto. The marinade, a fusion of olive oil, soy sauce, balsamic vinegar, and Dijon mustard, infuses the mushrooms with umami depth and a tangy kick, while the pesto—reminiscent of a classic basil version but with a wild, grassy zing—adds a fresh, herbal pop. Whether served as a vegetarian centerpiece alongside roasted vegetables or as a topping for crisp crostini, this dish captures the essence of Mediterranean-inspired grilling. For best results, use a high-quality oil sprayer to lightly coat the grill grates.
About This Recipe
Originating from a love of bold, rustic flavors, this Grilled Portobello with Arugula Pesto transforms a simple mushroom into a restaurant-worthy creation. The marinade, with its balanced blend of soy sauce, balsamic vinegar, and mustard, acts as a flavorful brine that tenderizes the caps while adding a caramelized crust during grilling. The pesto, made from fresh arugula, toasted walnuts, and garlic, offers a peppery bite that cuts through the richness of the mushroom. This dish is incredibly versatile—serve it as a main with a side of quinoa, a starter on a bed of mixed greens, or even tuck it into a crusty roll for a gourmet sandwich. The key lies in using a sturdy glass blender jar for the pesto to achieve a silky texture without overheating.
Ingredients
- 75 ml olive oil (for marinade)
- 45 ml soy sauce
- 30 ml balsamic vinegar
- 15 ml Dijon mustard
- 4 cloves garlic, minced
- 2 g dried oregano (about ½ tablespoon)
- 1 g freshly ground black pepper
- 1 g salt
- Pinch of chili flakes
- 4 large Portobello mushroom caps
- 100 g fresh arugula
- 80 g walnuts
- 2 cloves garlic (for pesto)
- 30 ml olive oil (for pesto)
- 15 ml lemon juice
- Salt and freshly ground black pepper to taste
Make sure your non-toxic immersion blender is ready for the pesto step.
Step-by-Step Instructions
1. Prepare the Marinade
Gently wipe the Portobello caps with paper towels to remove any dirt. In a large mixing bowl, whisk together 75 ml olive oil, 45 ml soy sauce, 30 ml balsamic vinegar, 15 ml Dijon mustard, minced garlic, dried oregano, black pepper, salt, and chili flakes until well combined. Place the mushroom caps in the bowl, turning them to coat thoroughly. Cover the bowl with plastic wrap and let them marinate at room temperature for 1 hour. This step is essential for infusing flavor; if you are short on time, a microwave pressure cooker can speed up the process, but traditional marinating yields deeper taste.
2. Toast the Walnuts
While the mushrooms marinate, heat a dry skillet over medium heat. Add the walnuts and toast them, stirring frequently, until they are golden and fragrant—about 2 minutes. Be careful not to burn them. Transfer the walnuts to a plate to cool. This toasting enhances their flavor and adds crunch to the pesto. Consider using a planetary mixer to crush them for a different texture, but a simple skillet works beautifully.
3. Make the Arugula Pesto
In a blender or food processor, combine the toasted walnuts, fresh arugula, 2 garlic cloves, 30 ml olive oil, 15 ml lemon juice, and a pinch of salt and pepper. Pulse until the mixture is smooth but still has a bit of texture—you may need to scrape down the sides once or twice. Taste and adjust seasoning. For the smoothest result, use a food processor designed for nut butter; it will handle walnuts effortlessly.
4. Grill the Portobellos
Preheat a grill pan or outdoor grill to medium-high heat. Remove the mushrooms from the marinade, allowing excess to drip off, and place them on the hot grill. Cook for 5 minutes on each side, until grill marks appear and the mushrooms are tender. Brush with a little reserved marinade if desired. For even cooking, ensure your grill surface is well-seasoned; a commercial countertop convection oven can also replicate grilling effects with a separate grill setting.
5. Slice and Serve
Transfer the grilled mushrooms to a cutting board. Let them rest for a minute, then slice each cap into 1–1.5 cm thick pieces. Arrange the slices on a serving plate, drizzle with any remaining marinade, and top each portion with a generous tablespoon of the arugula pesto. Serve immediately, while the mushrooms are still warm and the pesto is vibrant. Pair with crusty bread or a Catalan sponge cake for a surprising dessert contrast.
Tips for Perfect Grilled Portobellos
Choosing fresh, firm Portobellos is crucial—look for caps that are dry and free from slime. If your mushrooms are thick, consider scoring a shallow crosshatch pattern on the top to help the marinade penetrate. For a deeper smoky flavor, add a few wood chips to the grill or use a non-toxic air fryer with a grill function for a quick indoor version. The pesto can be made a day ahead; store it in an airtight container with a thin layer of olive oil on top to prevent browning. To keep the vibrant green color, squeeze a bit of extra lemon juice over the pesto before refrigerating.
Variations
This recipe is endlessly adaptable. Swap the arugula for baby spinach or kale for a milder pesto. Use pine nuts or almonds instead of walnuts for a different nutty note. For a dairy-free version, omit any cheese (the pesto is naturally cheese-free), or add a tablespoon of nutritional yeast for a savory kick. To turn this into a hearty main course, serve the mushrooms over creamy polenta or alongside a grain salad. If you prefer a sweeter marinade, replace the balsamic vinegar with a sweet wine with high alcohol content for a unique depth. For a touch of heat, increase the chili flakes or add a dash of hot sauce to the pesto.
Frequently Asked Questions
Can I use a different type of mushroom?
Yes, large cremini or shiitake caps work, but adjust grilling time accordingly. Portobellos are ideal for their size and meaty texture. For smaller mushrooms, reduce the marinating time to 30 minutes.
How do I make the pesto vegan?
This pesto recipe is already vegan—no cheese involved. If you want a richer texture, add a tablespoon of soaked cashews before blending. Consider using a high-quality organic vodka to deglaze the pan after grilling for an extra layer of flavor.
Can I prepare this dish ahead of time?
The mushrooms can be marinated up to 24 hours in advance (refrigerated). The pesto keeps for 3 days in the fridge. Grill the mushrooms just before serving to maintain their texture. Reheat slices briefly in a hot pan or under the broiler.
What sides pair well with this dish?
Try roasted asparagus, a crisp green salad with lemon vinaigrette, or creamy mashed potatoes. For a low-carb option, serve over sautéed spinach. A wheatgrass juicer can provide a fresh green juice to complete the meal.
How do I avoid watery mushrooms?
Do not wash Portobellos with water—wipe them with a damp paper towel. Also, make sure the grill is very hot so the mushrooms sear quickly, locking in moisture. Using a steam canner is not necessary, but it helps to understand the science of moisture retention.
