Peel the sweet potatoes (or scrub them well, if organic, and leave the skins on). Slice them somewhere between ¼ and ½ inch thick.
Arrange the sweet potato slices on a parchment-lined baking sheet or two, then bake for 15 minutes. Flip to the other side and bake for 10 minutes or so longer, until they’re starting to brown on the edges and are tender but not overdone. Remove from the oven.
While the sweet potatoes are roasting, heat the oil in a large skillet or steep-sided stir-fry pan. Add the onion and sauté until starting to turn golden. Add the garlic and continue to sauté until the onion is soft and golden.
Combine the onion and garlic mixture with the remaining ingredients for the sauce in a food processor and process until very smooth.
Combine the mushrooms and wine in the same skillet used for the onions. Cook over medium heat, covered, until the mushrooms are wilted, about 8 minutes.
Stir the tofu mixture from the food processor into the mushroom mixture in the pan, along with the parsley. Season the mixture with salt and pepper.
Spread a small amount of the mushroom sauce over the bottom of a shallow 9- by 13-inch casserole dish. Arrange one layer of 4 lasagne noodles over it, or enough to cover the surface.
Follow with a layer of half of the sweet potato slices, half of the optional cheese, and about a third of the mushroom sauce.
Follow with another layer of 4 noodles, the remaining half of the sweet potatoes the remaining half of the optional cheese, and another third of the mushroom sauce.
Top with and the remaining noodles. Finish with a layer of the remaining sauce. Sprinkle with some wheat germ or breadcrumbs and paprika. Don’t worry if you get some of these layers mixed up, it will all come out fine in the end!
Cover the lasagne loosely with foil and bake for 30 to 40 minutes, or until it’s easy to pierce the lasagne noodles through with a knife. Uncover and bake for 10 minutes longer. Let stand for 10 minutes, then cut into squares and serve.