use 2 tbsp. butter and 2 tbsp. flour, whisked together for about 2 minutes. Add 2 1/2 cups milk, and cook and stir frequently until thickened and bubbly. Remove from heat and stir in 1 pound (about 2 cups) sharp or extra-sharp cheddar. Season with salt and pepper to taste (I also like to add a few dashes of hot sauce).