Adjust racks to top and middle positions and preheat oven to 400 degrees. Bring a large pot of salted water to a boil. Reserve half the mozzarella in a small bowl. In a large bowl, soak half the panko (you’ll use the rest later) with 2 TBSP water (3 TBSP for 4 servings); let sit until absorbed (this’ll transform into a panade).

Add beef, half the Tuscan Heat Spice (you’ll use more later), 3/4 tsp salt (11/2 tsp for 4), and pepper to bowl with panade. Form into four 3-inch-wide rounds (eight rounds for 4); divide remaining mozzarella between the centers of each. Gently fold meat around cheese, shaping and sealing to create cheese-stuffed meatballs.

Lightly oil a baking sheet. Spread meatballs out on sheet. Bake on middle rack until cooked through, 20-22 minutes. (TIP: It’s OK if some cheese oozes out!) Remove from oven. Heat broiler to high.

Once water is boiling, add rigatoni to pot. Cook until al dente, 9-11 minutes. Reserve 1 cup pasta cooking water, then drain and set aside. Meanwhile, place 1 TBSP butter (2 TBSP for 4 servings) in second small microwavesafe bowl; microwave until melted, 30 seconds. Stir in remaining panko, 1/4 tsp Tuscan Heat Spice (1/2 tsp for 4; you’ll use the rest later), salt, and pepper.

Once meatballs and pasta are done, heat a large pan over medium-high heat. Stir in marinara, remaining Tuscan Heat Spice, 1/2 cup reserved pasta cooking water (3/4 cup for 4 servings), 1 tsp sugar (2 tsp for 4), and salt (we used 1/2 tsp; 1 tsp for 4). Bring to a simmer and cook until slightly thickened, 3-4 minutes. Remove from heat; stir in 1 TBSP butter (2 TBSP for 4). Season generously with salt and pepper.

Stir rigatoni and meatballs into sauce. If needed, stir in more reserved pasta cooking water a splash at a time until everything is thoroughly coated in sauce. (TIP: If your pan isn’t ovenproof, transfer mixture now to a 9-by-13-inch baking dish.) Top pasta with Parmesan, reserved mozzarella, and panko mixture. Broil until panko is golden brown and cheese has melted, 1-2 minutes. Let cool slightly; serve.