01 - Preheat the oven to 190 degrees Celsius (375 degrees Fahrenheit).
02 - Place the mushroom on a baking sheet and bake for 5 minutes in the preheated oven.
03 - Remove the mushroom from the oven and spread spaghetti sauce in the cup of the cap. Top with mozzarella cheese, sliced black olives, pepperoni, and chopped garlic.
04 - Bake for an additional 20 minutes or until the cheese is melted and golden.