Boil pasta in generously salted water until just shy of al dente. Before draining, reserve 1 cup of pasta cooking water.

Place chicken in a large bowl and toss with 2 Tablespoons of oil from the jar of roasted tomatoes (or 1 to 2 Tbsp. extra-virgin olive oil), Italian seasoning, paprika, ¾ tsp. salt, and ½ tsp. black pepper.Heat a large oven-safe skillet over medium heat. Add chicken and sauté until cooked through, about 8 minutes. Transfer to a bowl.

Add shallots to pan (along with an extra drizzle of oil, if needed) and cook until soft, about 3 minutes. Add garlic and red pepper flakes; cook until aromatic, about 1 minute. Stir in roasted tomatoes (or sun-dried tomatoes) and spinach. Cook until spinach wilts, about 2 to 3 minutes. Season with remaining ½ tsp. salt.Stir in pesto and heavy cream.

Add pasta and ½ cup of the reserved pasta cooking water. Stir continuously until the sauce thickens and clings to pasta. Stream in more pasta cooking water as needed until the sauce is thick and creamy (I usually end up using the full 1 cup). Stir in ⅓ cup of the Parmigiano-Reggiano cheese and cooked chicken.

Preheat oven broiler to HIGH. Scatter torn mozzarella cheese over pasta along with remaining Parmigiano-Reggiano cheese. Transfer pan under the broiler and broil until the mozzarella melts, about 3 to 4 minutes.Garnish with fresh basil and serve.