These Cheese-Stuffed Mushrooms are a long-time family favorite. Mushrooms are sauteed and then stuffed with Parmesan cheese, breadcrumbs, mushrooms and onions for a hearty, flavorful vegetarian appetizer that everyone will enjoy.
Preheat broiler. Line a baking sheet with parchment paper or foil and set aside.
Clean mushrooms and remove stems from caps. Trim tip of stem and discard. Finely chop the rest of the stem.
In same skillet, cook caps - cavity-side up- until browned and tender. Flip and cook until browned on other side. Transfer to a plate lined with paper towels to drain.
While mushrooms are cooking, add Parmesan cheese, bread crumbs, pepper, and milk to mushroom/onion mixture. Stir to combine. (If dry, add a teaspoon more milk. If too wet, add a teaspoon more breadcrumbs).
After mushrooms have been drained, arrange on the prepared baking sheet, cavities facing up. Stuff each mushroom with the prepared mixture.
Broil in preheated oven until browned, about 5-10 minutes. Garnish with chopped parsley, if desired. Serve immediately.