Cook your pasta, when it is about 1/2 way done get another pot melt your butter on low heat, when it is all melted put your 1/2 cup of flour in all at once and start whisking it with the flour to make a blonde rue. Cook for a couple minutes, then start whisking in your milk until it is all encorporated well. By this time your pasta should be done, drain it well and set aside for a sec. Now you want to season the mixture with the salt and pepper, then add your cheese, whisking to a creamy consistancy. Turn off heat, add pasta and stir until pasta is covered. Transfer to a greased casserole dish and Bake for 30 minutes, then I turn on broiler for a couple minutes to slightly brown it on top.