Preheat oven to 400 degrees. Coat a 9″ x 9″ baking dish with cooking spray. Set aside.
In a medium saucepan, cook pasta according to package directions. Place spinach in a large colander and set in the sink. Pour cooked pasta over spinach in colander; drain well. Set aside.
Place onions on a microwave safe plate and cooked in the microwave for about 2 minutes until soft. Heat 1 teaspoon oil in nonstick pan. Add onions and cook for a few minutes. Stir in flour, dry mustard, and pepper. Cook and stir for 1 minute. Gradually stir in evaporated milk. Cook and stir until slightly thickened. Continue to cook and stir for 1 more minute. Stir in cottage cheese and 3 tablespoons of the Parmesan. Mix until cheese is mostly melted. Gently stir in pasta/spinach and ham.
Add pasta mixture to baking pan. Sprinkle top with 2 tablespoons Parmesan cheese. Bake, uncovered, about 10 minutes or until the top starts to brown.
Cool for at least 10 minutes to slightly set. Cut into 4 squares. Use a spatula to remove each serving.
This casserole freezes great.