Cheesy Chicken Casserole with Broccoli and Bacon

INGREDIENTS

slices bacon (, chopped)

medium yellow onion (, diced)

3 cloves

garlic

1 1/2 cups

fresh broccoli florets

1/3 cup

butter

1/3 cup

all purpose flour

2 cups

whole milk

1 1/4 cups

half and half or heavy cream

2 1/2 cups

mozzarella cheese (, divided)

1/2 cup

shredded Parmesan cheese

16 oz

box dried medium pasta shells (, cooked according to package directions)

2 1/2 cups

shredded chicken

3/4 tsp

kosher salt

1/2 tsp

black pepper