Melt butter in a sauce pan over medium heat and stir in flour. Cook 1-2 minutes. Slowly add milk, stir well and stir again every few minutes. In about 10 minutes mixture will be smooth and thick. Season and add more milk, Mushroom Soup or Sherry to taste. Set sauce aside.
Saute ham, in a large skillet, with a dash of Olive oil over medium high heat until just starting to brown. Remove to cutting board and add mushrooms to skillet with another dash of Olive oil. When mushrooms are starting to brown add onion and cook until translucent. Remove vegetables to cutting board and give everything a rough chop.
Make filling by combining spinach, cottage cheese, 1/2 of Parmesan cheese and season to taste. Add ham and vegetables and about 1/3 cup of sauce.
Boil manicotti until slightly underdone, drain.
Spray 1 large or 2 medium casserole dishes and put enough sauce in the bottom of prepared casserole dishes to cover.
Assemble manicotti by stuffing with your fingers or using a small spoon. Lay the stuffed pasta on top of sauce in pan, closely together. Top with remaining sauce and sprinkle with remaining cheese.
Bake at 325 for about an hour if cold. If this dish is going straight to the oven start checking it after 30 minutes, it is done when it is bubbling and golden.