Begin by bringing a large pot of salted water to a boil. Cook spaghetti according to package instructions until al dente. Reserve ½ cup of pasta water before draining and setting aside.

In a medium saucepan, melt 2 tablespoons of butter over medium heat. Add minced garlic and cook until fragrant, about 30 seconds. Stir in the heavy cream and milk, whisking until smooth.

Reduce heat to low and gradually add shredded cheddar and grated Parmesan, stirring until melted and creamy. Season with Italian seasoning, salt, pepper, and crushed red pepper flakes (if using). Mix in the cooked spaghetti until well coated. If the sauce is too thick, add a splash of reserved pasta water to reach desired consistency.

While the pasta cooks, pat chicken strips dry and season generously with Italian seasoning, paprika, basil, salt, and pepper.

In a large skillet, heat olive oil and the remaining 3 tablespoons of butter over medium-high heat. Once hot, add chicken in a single layer and sear for 3–4 minutes on each side until golden brown and cooked through.

In the last minute of cooking, add minced garlic to the skillet and toss it with the chicken, allowing the garlic to infuse the butter.

Sprinkle shredded mozzarella over the chicken. Cover the skillet briefly to let the cheese melt slightly.

Plate the creamy spaghetti on one side and the garlic-herb mozzarella chicken on the other. Drizzle any remaining garlic butter from the skillet over the chicken. Garnish both parts with freshly chopped parsley.