Preheat the oven to 375 °F
Sauté Vegetables: Add butter or oil to a medium-sized skillet over medium heat. Once heated, add the onion and saute for 2-3 minutes. Mix in the minced garlic and continue cooking for an additional minute, or until fragrant.
2 Tbsp. butter, ¼ cup onion, 2 cloves garlic
Cook Sausage: Push the vegetables to the side of the skillet and add the sausage. Cook for 7-8 minutes, or until no longer pink. Crumble the cooked meat using a potato masher to break it apart into small pieces.
8 oz. sausage
Make Filling: Remove the skillet from the heat and mix in the cream cheese, mayonnaise, ¼ cup Parmesan cheese, paprika, red pepper flakes, salt, and pepper. Set aside until ready to use.
¼ cup mayonnaise, 4 oz. cream cheese, ¼ cup + 2 Tbsp. Parmesan cheese, ¼ tsp. paprika, ¼ tsp. red pepper flakes, ½ tsp. salt, ¼ tsp. black pepper
Prepare Mushrooms: Clean mushrooms with a damp paper towel to remove any dirt and debris. Remove the stems from the mushrooms by pulling them to one side and then snapping them off. You can also use a knife to cut them off if the stems do not snap easily. Place mushrooms on a large baking sheet that has been lined with parchment paper.
16 oz. mushrooms
Fill Mushrooms: Fill each mushroom cap with 1 to 1 ½ tablespoons of the sausage filling mixture. Pay careful attention not to fill them up with more filling than they are tall to prevent overflow while baking.
Top with Breadcrumbs: Whisk together the remaining tablespoon of butter and 2 tablespoons Parmesan cheese with the Panko breadcrumbs. Sprinkle about a teaspoon over each filled mushroom.
2 Tbsp. Panko breadcrumbs
Cook in Oven: Bake mushrooms in the preheated oven for 18-20 minutes, or until the tops become crispy and golden brown.
Serve stuffed mushrooms immediately with additional chopped parsley and enjoy!
2 Tbsp. parsley