Cook Elbows for 7 minutes. Add broccoli and contine cooking 2 additional minutes. Drain.
Mix together in empty pasta pot the cooked elbows, broccoli, 3 cups of mozzarella cheese, milk, 3/4 cup of Parmigiano cheese, onion, eggs and seasonings. (See Note below.).
Spoon into a lightly greased 13 x 9 inch baking dish. (If desired, you could spoon into 2 8" square pans and freeze one.).
Sprinkle with remaining Parmigiano and mozzarella cheeses. Cover and bake in a 350 degree oven for 40 minutes. Remove and let rest 10 minutes before serving.
NOTE: After mixing ingredients together in pot, sample a bit before spooning into baking dish(s). If you prefer more seasonings, you could add garlic powder or other seasonings you're in the mood for to taste.