Preheat Oven u0026 Prepare Noodles : Preheat oven to 375°F (190°C). Cook lasagna noodles according to package directions if not using no-boil noodles. Drain and set aside.
Make Pumpkin-Ricotta Mixture : In a medium bowl, combine pumpkin puree, ricotta cheese, Parmesan, minced garlic, chopped sage, nutmeg, salt, and black pepper. Mix until smooth.
Prepare Sauce (Optional) : If using béchamel or cream sauce, prepare according to recipe or package instructions.
Assemble Lasagna : Spread a thin layer of béchamel or sauce on the bottom of a 9x13-inch baking dish. Place a layer of noodles over the sauce. Spread 1/3 of the pumpkin-ricotta mixture over the noodles. Drizzle some béchamel/cream sauce and sprinkle 1/3 of mozzarella. Repeat layers 2–3 times, finishing with a layer of noodles, pumpkin mixture, sauce, and mozzarella on top.
Bake : Cover with foil and bake for 25 minutes. Remove foil and bake an additional 10–15 minutes until top is golden and bubbly.
Rest u0026 Garnish : Let lasagna rest 10 minutes before slicing. Garnish with fresh sage leaves.