If roasting, preheat oven to 375 degrees or start your grill if grilling the mushrooms.
Clean the mushroom caps with a damp paper towel by wiping any dirt off them.
Remove stems and save stem pieces. Chop stems and set aside.
Drizzle 1 tbsp olive oil on mushroom caps, toss mushrooms in the oil, and rub oil on both the outside and inside of the cap.
Sprinkle 1/4 tsp kosher salt and a couple turns of fresh ground pepper on the mushrooms.
Empty caps can either be roasted at 375 degrees for 7 minutes or grilled for 3 minutes per side.
Place the caps gill-side down if roasting. If grilling, they will be grilled on each side.
When the initial cooking process is complete, it's a good idea to empty any liquid that has pooled in the cap. You don't want too much moisture left in the portobello caps when you stuff them.
Meanwhile sauté the chopped stems in 1 tbsp olive oil with minced garlic clove for approximately 7-9 minutes until stems are reduced and fully cooked.
While cooking sprinkle with a dash of kosher salt and freshly cracked black pepper. If you like a bit of extra spice and have chosen to use the optional red pepper flakes, sprinkle and sauté with the stems and garlic.
In a small bowl, combine the ricotta cheese, shredded mozzarella/provolone cheese, parmesan cheese, fresh herbs and ¼ tsp kosher salt and a few turns of freshly ground pepper.
Once the sautéed stems and garlic mixture is cooked and cooled, combine with the cheese mixture.
Stuff the roasted / grilled mushroom caps.
Place mushroom caps on a rimmed baking sheet with aluminum foil for easy cleanup and return to the oven (or grill) for 5 minutes until the mushrooms are warmed through and golden brown.
Or if you used the grill and don’t want to start your oven, you can return the stuffed mushrooms to the grill for 5 minutes to warm through.
Enjoy!