Preheat oven to 400 degrees F. Place butternut squash on a baking sheet and toss with salt, pepper, nutmeg and olive oil. Roast for 20 minutes, flip, then roast for 20 minutes more. Remove from oven and mash with a fork or potato masher until almost pureed.

Boil water and prepare shells according to directions. Mine called for 9 minutes. Drain pasta and set aside to cool. While pasta is cooking, heat a small saucepan over medium heat and add 2 tablespoons butter, garlic and shallots. Whisk until brown bits appear in the butter, then mash into the butternut squash, along with the mascarpone and and tablespoon of parmesan. Spray a baking dish (8×8) or pie plate with nonstick spray. Spoon about 1 1/2-2 tablespoons (depending on the size of your shells) of squash into each shell, then lay in the dish. Repeat.

To make the bechemal, heat a saucepan over medium heat and add butter. Once sizzling, whisk in flour and cook until golden and a nutty aroma appears. Add milk and parmesan and let come to a simmer while whisking constantly. Once sauce has thickened, stir in nutmeg and taste – add salt and pepper if desired. Pour mixture over top of shells, then add mozzarella and sage. Bake at 400 degrees F for 20-25 minutes, or until cheese is golden and bubbly.