In a saucepan melt butter over low heat. Add flour and stir (using a wooden spoon). In a separate saucepan have hot stock over low to medium heat. While constantly whisking, gradually add hot stock to the roux (the butter and flour mixture). Simmer mixture while continuing to whisk. Sauce will thicken in a few minutes. ***To basic finished veloute sauce, add 1 cup sauteed mushrooms, Tabasco, and 1/4 cup grated Parmesan. Toss with pasta. Garnish with parsley.