While the broiler is preheat, slice the mini san marzano tomatoes in half. Toss with olive oil, garlic, salt, and pepper. Add to an oven safe casserole dish. Broil for 10 minutes.
Remove the broiled tomatoes from the oven, mix tomatoes, then add in the ½ cup of fresh mozzarella. Broil for 2 minutes.
While tomato/mozzarella mixture is under the broiler mix 1 tablespoon melted butter with 1 tablespoon of olive oil. Add panko bread crumbs and set to the side.
Remove tomato/mozzarella mixture from the oven, add half the fresh basil to the dish, then top with panko bread crumbs. Top with 1 tablespoon shredded parmesan cheese. Broil an additional 1-2 minutes until panko topping is golden brown. Before serving, sprinkle the remaining basil on top of the casserole.