• Prep Mushrooms: Clean mushrooms by wiping with a damp paper towel or a mushroom brush. Using your hands, remove stems and set aside (don’t discard stems).
• Marinate Mushroom Caps: Transfer mushroom caps to a large mixing bowl and toss with vinegar and oil. Set aside.
• Preheat Oven: Preheat oven to 375 degrees F (190 degrees C). Pull out and set aside a 9x13-inch baking pan.
• Cook Sausage: To a large skillet over medium heat, add ground sausage and cook until it’s browned and cooked through, breaking into small pieces as it cooks. This usually takes 5-7 minutes.
• Chop Mushroom Stems: While sausage is cooking, finely chop mushroom stems.
• Remove Excess Grease: Remove skillet from heat and use a paper towel to blot away any excess grease from the sausage. Alternatively, transfer sausage to a paper towel-lined plate.
• Prepare Sausage Filling: To a mixing bowl, add cooked sausage, chopped mushroom stems, softened cream cheese, breadcrumbs, Parmesan cheese, minced garlic, parsley, salt, and pepper. Mix everything until it reaches the consistency of a stuffing.
• Stuff Mushrooms: Take each marinated mushroom cap and use a small spoon to stuff them generously with sausage mixture, pressing it in gently, to form a small mound. Then, transfer each stuffed mushroom to your baking pan.
• Bake Stuffed Mushrooms: Transfer baking pan to the oven and bake for about 20-25 minutes, or until mushrooms are tender and the stuffing is golden brown on top.
• Serve: Remove baking sheet from the oven and let mushrooms cool for a few minutes before serving on a serving platter.

TO PREPARE IN ADVANCE:

• Prepare Filling (1-2 Days in Advance): Cook sausage, mix it with cream cheese, breadcrumbs, Parmesan cheese, minced garlic, parsley, salt, and pepper. Once mixed, transfer filling to an airtight container and refrigerate.
• Clean Mushrooms (1 Day in Advance): Clean and remove the stems from the mushrooms. Store cleaned mushroom caps in a paper towel-lined container or a plastic bag and refrigerate.
• Stuff Mushrooms (Day Of): Take prepared filling and cleaned mushroom caps out of the refrigerator, then marinate for 10-15 minutes in vinegar and oil. Stuff the marinated mushrooms with filling.Stuff mushrooms with filling.
• Bake (Day Of): Preheat oven to 375 degrees F (190 degrees C) and bake the stuffed mushrooms as instructed (see Step #9 above). You may need to add a few extra minutes to the baking time to account for the cold filling and mushrooms.