Cheesy Italian Burgers with Pizza Toppings (Skillet Dinner)

Ingredients

• 1 lb (450 g) 80/20 ground beef
• 4 oz (115 g) mild Italian sausage, casing removed
• 1 teaspoon Italian seasoning
• 3/4 teaspoon kosher salt
• 1/2 teaspoon black pepper
• 4 brioche or potato burger buns, split
• 2 tablespoons unsalted butter
• 1 garlic clove, finely grated or minced
• 1 tablespoon olive oil
• 3/4 cup (180 ml) thick marinara or pizza sauce, warmed
• 1 cup (115 g) shredded low-moisture mozzarella
• 24 pepperoni slices
• 1/2 cup (55 g) thinly sliced mushrooms
• 1/3 cup (45 g) thinly sliced bell pepper
• 1/4 cup (30 g) thinly sliced red onion
• 2 tablespoons grated parmesan
• 2 tablespoons torn fresh basil