12 ounces dried rigatoni
1 1/2 pounds butternut squash, peeled, seeded and cut into chunks (3 1/2 cups)
2 3/4 cups milk
1/4 cup all-purpose flour
8 ounces smoked Gruyere cheese, shredded (2 cups)
8 slices bacon
2 small sweet onions, cut into chunks
3 ounces sourdough bread
2 tablespoons butter, melted
fresh flat-leaf Italian parsley
Preheat the oven to 425 degrees F. Lightly butter a 3-quart au gratin or baking dish; set aside. Cook pasta according to package directions. Drain; transfer to a large bowl.
Meanwhile, in a large saucepan combine the squash and 2 1/2 cups of the milk over medium-high heat. Bring to boiling; reduce heat to medium, and simmer until the squash is tender when pierced with a fork, 18 to 20 minutes. Stir together remaining 1/4 cup milk and flour; stir into squash mixture. Bring to boiling; cook until thickened, 2 to 3 minutes. Stir in 1 1/2 cups of the Gruyere until melted; keep warm.
Meanwhile, in a very large skillet cook bacon until crisp; drain on paper towels. Crumble; set aside. Pour off all but 2 tablespoons bacon drippings. Return skillet to the heat.
Add onions to skillet; cover and cook over low heat 10 minutes, stirring occasionally. Uncover and increase heat to high. Cook 4 to 6 minutes more, stirring, until onions are golden.
Add squash-cheese mixture, onions, and bacon to the bowl with the pasta. Toss well to combine, then transfer to prepared baking dish.
Place bread in a food processor and pulse with two or three on/off turns to form large coarse crumbs (you should have about 2 cups). Transfer to a small bowl; mix with melted butter. Sprinkle remaining Gruyere and the bread crumbs over pasta mixture. over Bake until top is browned, about 14 to 15 minutes. Cool 5 minutes. Sprinkle with parsley. Makes 6 to 8 servings.