Bring a large pot of well-salted water to a boil. Cook rigatoni until just al dente per package directions. Reserve 1/2 cup pasta water, then drain and set aside.

Meanwhile, toss chicken with olive oil, garlic powder, salt, black pepper, and Italian seasoning.

Heat a large skillet over medium-high. Add the seasoned chicken in a single layer and cook 5–7 minutes, stirring once or twice, until lightly golden and cooked through. Transfer chicken to a plate and keep warm.

Reduce heat to medium. In the same skillet, add butter and minced garlic; cook 1–2 minutes until fragrant (do not brown).

Pour in heavy cream and milk; stir and bring to a gentle simmer.

Add cubed Velveeta; stir until completely melted and smooth. Sprinkle in mozzarella (and parmesan, if using) and whisk until the sauce is creamy. If too thick, loosen with splashes of reserved pasta water.

Return cooked chicken to the skillet and add the drained rigatoni. Toss gently to coat every piece in the sauce; simmer 1–2 minutes to meld flavors. Taste and adjust salt and pepper.

Garnish with chopped parsley or basil. Serve hot; add optional red pepper flakes or fold in spinach or mushrooms if desired.