This recipe is slightly adapted (more spinach, asiago cheese instead of parmesan, and panko instead of homemade breadcrumbs) from one published by Cooking Light in 2007. It received rave reviews online, but I was very disappointed as it was really lacking in flavor - it tasted mostly like a thick roux with very little of the pancetta or garlic coming through. Just goes to show that you can't always rely on other people's opinions.
3/4 cup (3 ounces) chopped pancetta
3/4 cup chopped onion
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 packed, chopped fresh spinach
1/2 cup grated fresh Parmesan (or Asiago) cheese
1 1/4 teaspoons salt
1/2 teaspoon black pepper
1 lb cooked penne pasta
1 cup bread crumbs
1/4 cup butter, melted
Preheat oven to 425°.
Heat a large nonstick saucepan over medium-high heat. Coat with cooking spray. Add pancetta, onion, and garlic; sauté 5 minutes or until onion is tender. Place flour in a small bowl; gradually add 3/4 cup milk, stirring until smooth. Add flour mixture, remaining 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 13 x 9-inch baking dish coated with cooking spray. Add sauce mixture to pasta; toss well. Combine breadcrumbs and butter; toss well. Sprinkle over pasta mixture. Bake at 425° for 6 minutes or until crumbs are lightly browned.