Heat olive oil in a large skillet over medium heat. Add chicken and cook, flipping once, until cooked through, about 4-5 minutes on each side; set aside.
Add garlic to the skillet, and cook, stirring frequently, until fragrant, about 1-2 minutes.
Stir in crushed tomatoes, basil, oregano, parsley and red pepper flakes; season with salt and pepper, to taste.
Bring to a boil; reduce heat to low and simmer, stirring occasionally, until sauce has thickened, about 15-20 minutes.
Return chicken to the skillet. Top with mozzarella and mini pepperonis.
Place into oven and cook until melted and golden brown, about 2 minutes.
Serve immediately, garnished with basil, if desired.