Preheat oven to 375°. Lightly oil a 9×13-inch ceramic baking dish.
Place cottage cheese and egg in a blender; puree until smooth. Scoop into a bowl, and set aside.
Heat 2 tablespoons oil in a skillet; add onions and sauté over medium heat, until soft. Add garlic and spinach a handful at a time. Cook until wilted; remove from pan.
Raise heat to high, and add mushrooms. Brown evenly, and add sun-dried tomatoes; cook until fragrant. Add spinach back to pan, stir well, and add cream. Bring to a boil, and reduce heat. Add cottage cheese mixture to the pan. Stir well, and remove from heat
Heat remaining oil in a medium sauce pan over medium-high heat; add flour and stir with a whisk for 6–10 minutes, until lightly toasted. Gradually add a little milk at a time, whisking well each time. Stir until thickened; let edges bubble, but do not boil. Add nutmeg, one-quarter of both cheeses, salt and pepper, and stir well. Pour this mixture into spinach, and combine. It may be a little stringy.
Place a single layer of noodles, edge to edge, in bottom of pan to cover. Spoon out one-third of spinach mixture over noodles; top with one-third of the mozzarella. Repeat with a layer of noodles, spinach, cheese and a last noodle layer.
Top with remaining spinach and cheeses. Bake 30–40 minutes, until noodles are soft and sauce is bubbly.