Step 1

Preheat the oven to 375°F.

Step 2

Cook the spaghetti according to the package instructions (until al dente and still slightly firm). Drain and set aside.

Step 3

In a large skillet over medium-high heat, cook the garlic and bell pepper in the butter until tender. Stir in the flour and Italian seasoning, and cook for 1 minute more.

Step 4

Stir in the heavy whipping cream, broth, and milk. Bring the pan to a boil, reduce the heat and simmer until it begins to thicken.

Step 5

Remove the pan from heat and stir in ½ cup of mozzarella until combined. Season with salt and pepper.

Step 6

Stir the spaghetti, chicken, and diced tomatoes into the pan. Spread the mixture into a lightly greased 9x13 baking dish.

Step 7

Top with the remaining mozzarella and bake for 15-20 minutes, until the edges are lightly browned and the cheese is bubbly.