To make baked stuffed mushroom appetizers, prepare a filling consisting of a mixture of herbs and onions. Stuff the mixture into the mushroom cups, arrange them in a baking dish and bake in a preheated oven.
Preheat the oven to 350 F. In a medium-sized bowl, combine 5 sliced green onions, 1/4 teaspoon of thyme, and 1/4 teaspoon of ground oregano or mint. Add black pepper and salt to taste. Add 1/4 cup of grated parmesan cheese to the mixture. Blend the mixture with a plastic or wooden spoon, and then cover it with plastic wrap and set it aside.
Choose mushrooms that are about 2 inches across to hold the filling. Use a damp cloth to wipe the mushrooms clean and gently remove the stems. Spoon the gills out of the mushrooms to make the cups.
Fill the mushroom cups with the stuffing mixture and place them in a shallow baking dish. Sprinkle some grated cheese on the stuffed mushrooms and dust with paprika. For crispier mushrooms, top them with breadcrumbs. Place the baking dish in the oven for 15 to 20 minutes or until some moisture appears under the caps. Once ready, serve the stuffed mushrooms while hot.