If you've heard about the Engine 2 Diet and want to try an Engine 2 approved recipe, here's a sample recipe to try. This is Rip Esselstyn's "Raise the Roof" sweet potato vegetarian lasagna. It's so good, he says, that he served it at his own wedding! It's also low in fat and cholesterol-free. Recipe courtesy of The Engine 2 Diet, by Rip Esselstyn. When I made this recipe, I only needed one box of lasagne noodles because the veggie mixture was so plentiful that I couldn't fit in another…