Start by cleaning your mushrooms with a mushroom brush or a paper towel. Carefully remove the stems and set them aside. Place the mushroom caps, top side down, in an oven-safe casserole dish. Finely chop the mushroom stems, green onion, and garlic.

In a small saucepan, heat 2 tablespoons of olive oil and 2 tablespoons of butter over medium heat. Add the chopped mushroom stems, garlic, and green onion, and sauté for 1-2 minutes. Then, add the juice of half a lemon and 1/4 cup of dry sherry. Continue to sauté until about 60% of the liquid has evaporated. Set this mixture aside to cool.

In the same saucepan, add 1 cup of dry sherry, the juice of the remaining half of the lemon, and 2 more tablespoons of butter. Let this mixture reduce by half over medium heat, then remove from heat and set aside.

In a mixing bowl, combine 1 cup of seasoned bread crumbs, 1/2 cup of grated Parmesan cheese, 1/2 cup of grated Fontina cheese, and 1 teaspoon of finely chopped parsley. Add a pinch of salt and about six cranks of black pepper. Once the sautéed mushroom mixture has cooled, combine it with the dry ingredients. Mix well, ensuring the bread crumbs are evenly moistened.

Using a 2-ounce melon baller or small scoop, firmly pack the stuffing mixture into the scooper and release it onto each mushroom cap. Press gently to ensure the filling stays in place.

Preheat your oven to 350°F (175°C). Spoon the reduced wine sauce over the stuffed mushrooms. Bake for 8-10 minutes, or until the mushrooms are tender and the stuffing is golden.

Once out of the oven, sprinkle the mushrooms with fresh parsley. Let them cool slightly before serving, as they’ll be very hot. Enjoy this classic appetizer from the comfort of your home!