Place butter into sauce pan and melt on medium heat, whisk in flour (it will be lumpy) next whisk in heavy cream or creamer, mustard, and cheese continually stirring and bring to a rolling boil. Sauce will be thick set aside.
In the meantime boil a 12 ounce box of macaroni according to directions.
Defrost spinach in microwave according to package directions (for fresh prepare accordingly).
In a large sauté pan add cup of olive oil and heat on medium heat. Add olives, peppers, and spinach sauté for about five minutes till all ingredients are tender.
Once all ingredients are tender, pour cooked pasta and vegetable mixture into a well-greased casserole dish. Add sauce and stir combining ingredients.
Top with the cup of Feta cheese and bake uncovered for 15 minutes. Serve with salad.