Preheat oven to 350 F degrees. In a large, oven-safe skillet, cook bacon over MED heat until crisp. Remove to a plate, reserving grease in skillet. Remove all but 1 Tbsp of the bacon grease.
To the same skillet, add diced onion and cook 4-5 minutes, until soft. Add garlic and cook 1 minute, stirring very often. Remove to plate with the bacon.
Add broccoli to skillet and cook 2-3 minutes, until very bright green and heated through. Remove to plate.
Add butter and melt, then add flour and whisk to combine. Slowly pour in milk and half and half, whisking until all flour mixture is incorporated. Cook, whisking very often, until mixture has thickened (about 5-10 minutes).
Remove from heat and stir in 1 3/4 cups of mozzarella cheese and the 1/2 cup of Parmesan cheese until melted.
Add in cooked pasta, shredded chicken, bacon, onion, broccoli, salt and pepper. Stir until combined. Top with remaining 3/4 cup of mozzarella cheese.
Bake 15 minutes, then broil on HIGH for 1-2 minutes to brown cheese (optional). Serve hot and enjoy!