Heat oven to 350 degrees. Mist inside of a 2-quart covered casserole dish (roughly 10 by 10 inch) with non-stick spray; set dish aside.
Cook pasta in boiling salted water for length of time package specifies until it is al dente (firm to the bite). (The pasta will cook for additional time in the oven, so dont overcook it to mushiness at this point.)
Meanwhile, in a large skillet, add 1 tablespoon water and spinach leaves. Wilt spinach over high heat, tossing several times until greens cook down. This will take only 3-5 minutes. When wilted, remove pan from heat and set aside.
While pasta is cooking, in a large mixing bowl beat egg with a fork. Add cottage cheese, milk, 2 tablespoons of the Parmesan, onion, garlic, nutmeg and a pinch of salt and pepper. Stir to combine. Add cooked spinach, Jack cheese and cooked (drained) pasta. Stir to mix well.
Turn into prepared pan, sprinkle with remaining 2 tablespoons of Parmesan, cover and bake 15 minutes. Uncover and bake 20 minutes longer. Remove from oven and serve.
This recipe saves well in the refrigerator and reheats well in the microwave the next day.
Ingredient substitution note: If you dont have cottage cheese, you may substitute sour cream (regular, low- or non-fat). You may also substitute another favorite variety of greens for the spinach.