This recipe is pretty straightforward and simple and best of all - it's absolutely scrumptious. Make it for your next gathering and your friends and family will love them.
Preheat the oven to 400˚F. Line a large baking sheet with parchment paper.
Remove the stems from mushrooms. Discard the tips of stems, then chop the remaining stems.
Heat 2 tablespoons of the olive oil in a small skillet over medium heat. Add the chopped mushroom stems, garlic, and onion. Stirring often, sauté until the mushroom stems are tender, about 7 minutes. Transfer to a medium bowl. Add the prosciutto, breadcrumbs, parsley, 1/4 cup of the Parmigiano, egg, salt and pepper. Mix well to combine.
Divide the filling among the mushroom caps, heaping slightly. Arrange the mushrooms in one layer on the baking sheet. Sprinkle the stuffed mushrooms with the remaining cheese and drizzle with the remaining 2 tablespoons of olive oil. Bake until tender, about 20 to 25 minutes.