INGREDIENTS:
- 3 ounces mozzarella cheese, shredded (about ¾ cup)
- 2 ounces pepperoni slices, cut in quarters
- 1 teaspoon chopped fresh oregano
- ¾ cup pizza sauce, divided
- 1 ¼ pounds 85/15 ground round beef
- ½ teaspoon kosher salt
- ½ teaspoon black pepper
- ¾ cup sautéed mushrooms
- 4 (¾-ounce) mozzarella cheese slices
- 1 tablespoon olive oil
- 1 teaspoon minced garlic
- 4 French hamburger buns, toasted
- 16 fresh basil leaves
- 8 pitted black olives
- 4 pickled pepperoncini peppers