Preheat the oven to 375°F. Lightly grease a 9x13-inch baking dish or 12-inch round cast iron skillet.
For the Pesto Spinach Ricotta:
In a small skillet over medium heat, sauté the onion in 1 tablespoon of olive oil for 2-3 minutes, or until translucent.
Add silken tofu, cashews, lemon juice, nutritional yeast, garlic, miso, and salt to a food processor. Blend on high until the mixture is smooth, scraping down the sides, as needed. Add the pesto, spinach, and sautéed onions. Pulse just until the spinach and onions are distributed throughout the mixture, but texture remains.
Add the ricotta to a large piping bag (or medium freezer bag). Twist the bag closed, and secure with a twist tie (or zip shut if it’s a bag).
For the Pumpkin Alfredo Sauce:
In a blender, combine all the ingredients for the sauce and blend on high until completely smooth.
To Assemble:
Pour about 3 cups (750 mL) of the pumpkin alfredo sauce into the baking dish. Snip off the end of the bag containing the ricotta so you have a ½-inch opening. Gently squeeze the ricotta into each shell. Place the shells into the sauce as you go. Once the shells are filled, carefully spoon the remaining alfredo sauce over the shells. Cover the baking dish tightly with aluminum foil. Bake for about an hour, or until the center is bubbling and the shells are al dente. When ready to serve, drizzle ¼ cup of pesto over the top and top with fresh basil leaves.
Notes
*If you have a high-powered blender, you may skip soaking the cashews. If short on time and you don’t have a high-powered blender, you may quick-soak the cashews by covering them with water in a small pot and simmer them for about 15 minutes.Note: This dish may be prepared ahead, covered, and refrigerated until you're ready to bake it. Baking time may be reduced by about 10 minutes, as the noodles will have softened by soaking in the sauce in the fridge.