Melt 3 tablespoons butter in a medium nonstick pan over medium heat. Add sage and stir for 30 seconds. Add panko and a small pinch of salt. Stir constantly until the breadcrumbs are golden and toasted. Watch closely to avoid burning.
Transfer immediately to a bowl to stop cooking. Once cooled, discard the sage and stir in the Parmesan. Set aside.
Bring 12 cups of water to a boil in a large pot. Once boiling, stir in 1 tablespoon fine sea salt and the rigatoni. Cook according to package directions. Before draining, scoop out a mug of pasta water and set aside. Do not rinse the pasta.
While pasta cooks, melt 2 tablespoons butter in a large pot over medium heat. Add diced onion and sauté until softened, about 4 to 5 minutes. Stir in garlic and cook for 30 seconds until fragrant.Add chicken broth and pumpkin. Whisk until smooth. Lower heat and stir in heavy cream and Parmesan. Season to taste (I add 1 tsp salt and 1/2 tsp pepper). Simmer, stirring occasionally, until sauce thickens slightly (see note 3).
Dump the drained pasta directly from the colander into the sauce and gently toss for about 2 minutes or until the sauce thickens and nicely coats the pasta. Sauce shouldn’t be falling to the bottom of the pot. If the sauce is too thick, add a splash of that reserved pasta water.
Divide pasta into bowls, top with a generous spoonful of the crunchy topping, and serve immediately.
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Notes
Note 1: Use only 100% pure pumpkin purée, not pumpkin pie filling. Measure out 1 cup; don’t use the whole can.Note 2: Pre-grated Parmesan (especially the kind in a can) is too salty and doesn’t melt well. For best results, grate a block of Parmesan cheese on the small holes of the grater (or on a microplane) for ultra-fine cheese shreds.Note 3: To check if the sauce is ready, dip a spoon in and run your finger across the back. If the line stays visible, the sauce is thickened enough.Storage: This pasta is best enjoyed right after tossing with the sauce. To store leftovers, refrigerate in an airtight container. Add a splash of cream or broth when reheating to loosen the sauce. The texture will be softer but still flavorful. This recipe isn’t ideal for freezing due to the dairy and pasta.