In a medium size bowl, crumble up the tofu with your hands. Add the lemon juice, garlic, salt, nutmeg and pepper. Continue to work the mixture with your hands, until the ingredients are evenly incorporated. Set aside.
In a small pan over medium-high heat, toast the pine nuts in a single layer, stirring frequently, for 3 - 4 minutes or until they are just lightly browned. Remove from heat.
In a food processor, grind the pine nuts for a few seconds. Add 1 tablespoon of olive oil and process the pine nuts until smooth, about 1 - 2 minutes. Add the basil leaves and the spinach to the food processor and pulse a few times until finely chopped. Add the tofu ricotta mixture to the food processor, and blend everything to a smooth consistency, scraping the sides often and adding more oil if necessary. Transfer mixture to a separate container, cover, and refrigerate until ready to use.
Preheat the oven to 350°.
Bring a large pot of water to a rolling boil. Stir in the conchiglioni, a very generous pinch of salt (optional), and about a tablespoon of olive oil. Cook the pasta al dente, for about 9 - 10 minutes (or according to package directions), stirring occasionally to prevent sticking. Drain shells, lay them out on a clean towel and allow them to cool before handling.
Lightly grease a casserole dish and coat the bottom with a layer of tomato sauce. Fill each pasta shell with approximately 2 tablespoons of the tofu ricotta mixture and squeeze each shell gently to seal shut. Place shells in the casserole dish and cover with the remaining sauce.
Cover the dish with aluminum foil and bake for 20 minutes. Serve with warm garlic bread and sautéed veggies.