Cook the pasta shells according to the instructions on the pack.
Finely cut the spinach; use a food processor if you have one. Fry it gently with the nutmeg until softened. Add salt and pepper to taste.
In a bowl crumble the tofu into small pieces and mix in the oil, vinegar, lemon juice, salt and pepper. Add to the spinach and fry for a couple of minutes.
Lightly coat the base of an oven-proof dish with olive oil. Place some of the mixture inside each pasta shell and place in a single layer in the dish. Spoon the tomato sauce over the shells then place in the oven and bake for 15 minutes.