Bring a large pot of salted water to a boil. Cook the 8 oz penne until al dente, about 1 minute less than package directions. Drain and set aside.

Season the chicken with the ½ tsp salt and ¼ tsp pepper. In a large skillet with a drizzle of oil over medium-high heat, cook the chicken until browned and cooked through, about 5-6 minutes. Transfer to a plate.

Lower heat to medium. Melt the 2 tbsp butter, then cook the 3 minced garlic cloves for 30 seconds. Whisk in the 2 tbsp flour and cook 1 minute. Slowly whisk in the 1 ½ cups milk and ½ cup cream. Simmer, stirring, until thickened, about 2 minutes. Remove from heat. Stir in the 1 cup Parmesan and a pinch of nutmeg.

Preheat oven to 375°F (190°C). Toss the drained pasta and chicken with the sauce. Spread into a greased 2 quart baking dish and top with the 1 cup mozzarella.

Bake for about 20 minutes until bubbly and golden. Let rest a few minutes, then serve.