Light Cheese Sauce

Whisk flour with 1/4 cup milk in a small bowl until smooth. Heat the remaining milk in a small saucepan over medium-low heat until steaming. Add the flour mixture and cook, whisking constantly, until the sauce bubbles and thickens, about 4 minutes. Remove from the heat; stir in Cheddar, dry mustard, paprika, cayenne (if using) and salt.