1
Remove the stems from the mushrooms. Chop the stems and set the caps aside.
2
Cook the onion and chopped mushrooms in olive oil, followed by the garlic. Remove from heat.
3
Combine the panko, Parmesan, parsley, thyme, lemon zest, salt, and red pepper flakes. Stir in the cooked mushroom mixture. Spoon the filling into the mushroom caps, then drizzle with olive oil.
4
Bake and serve.