Source: MIT German House
Preheat oven to 400° F. Set aside one cup of mozzarella cheese for later user. Mix sauce, water, ricotta, Parmesan, and remaining mozzarella cheese, combining well. Stir in dry pasta. Pour into a 13x9 baking dish. Cover tightly with foil and bake for 55 to 65 minutes. Remove from oven and sprinkle remaining mozzarella on top. Bake uncovered for 5 to 20 minutes, to your taste.
Ricotta cheese is approximately 50% to 75% water. I have found that, if you run out of ricotta, you can substitute it with water and more cheese or other solids (mushrooms, meat, etc.) When I tried it, I put in about 7.5 oz. of water in addition to the water already called for, then added a little extra cheese. This seemed to work fine, although it is not quite so tasty.
This dish is good with ground lamb, slightly browned beforehand—makes it into a sort of cheap sort of fake pastitsio, well, if you really pretend.
Another variation is to add spinach into the mixture. Spinach is approximately 92% water, so adjust the water content accordingly. You can use either frozen spinach (steam it or microwave it first), or you can use fresh spinach.
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