Preheat the oven to 180°C. Spray an 18x28 cm glass baking dish with cooking spray. Cook the lasagne sheets in a large saucepan of boiling water according to the packet directions, until firm-tender. Drain.
Meanwhile, heat the oil in a large nonstick frying pan over moderate heat. Add the onion and garlic and cook for 5 minutes or until soft. Add the mushrooms and cook for 4 minutes. Add the spinach and cook, stirring, for 5 minutes or until no liquid remains. Transfer to a medium bowl and add the lemon zest, a pinch of salt and a good grinding of pepper. Toss well.
Combine the tofu, cottage cheese, ricotta cheese, 4 tablespoons of the Parmesan, the pasta sauce, tomato paste, whole egg and egg whites in a food processor. Process to a smooth purée.
Line the bottom of the prepared baking dish with 2 of the lasagne sheets. Spoon half the spinach mixture and a third of the tofu mixture over the pasta. Make another layer of pasta, the remaining spinach mixture, and another third of the tofu mixture. Top with the remaining lasagne sheets and the remaining tofu mixture. Sprinkle the remaining Parmesan on top. Bake for 30 minutes or until hot.