This is good, but it's not cheesy.
8 ounces French bread
3/4 cup (3 ounces) chopped bacon
2 teaspoons minced garlic
1/3 cup all-purpose flour (about 1 1/2 ounces)
3 3/4 cups 2% reduced-fat milk, divided
1/4 cup half-and-half
6 cups chopped fresh spinach
1/2 cup (2 ounces) grated fresh Parmigiano-Reggiano cheese
1 1/4 teaspoons salt
1/2 teaspoon black pepper
8 cups hot cooked penne (about 1 pound uncooked tube-shaped pasta)
1/4 cup butter, melted
Preheat oven to 425°.
Place bread in a food processor; pulse 10 times or until coarse crumbs measure 4 cups; set aside.
Heat a large nonstick saucepan over medium-high heat. Coat with cooking spray. Add bacon and garlic; sauté 5 minutes. Lightly spoon flour into a dry measuring cup; level with a knife. Place flour in a small bowl; gradually add 3/4 cup milk, stirring until smooth. Add flour mixture, remaining 3 cups milk, and half-and-half to pan; bring to a boil, stirring constantly. Reduce heat, and simmer 2 minutes or until thick, stirring constantly. Add spinach; cook 1 minute. Remove from heat. Stir in cheese, salt, and pepper, stirring until cheese melts.
Place pasta in a large bowl. Add sauce mixture to pasta; toss well. Spoon mixture into a 13 x 9-inch baking dish coated with cooking spray. Combine breadcrumbs and butter; toss well. Sprinkle over pasta mixture.
Bake at 425° for 6 minutes or until crumbs are lightly browned.
--Adapted from Cooking Light magazine