In a 2 cup, non-metallic measuring cup melt butter in Microwave Oven for 30 seconds. Add light cream, egg yolks, vinegar, salt, cayenne and mustard; stir to blend thoroughly. Heat, uncovered, in Microwave Oven for 1 minute or until thickened. Stir frequently. Be careful not to overcook as sauce will curdle. Beat the sauce until light and fluffy. Set aside. Place the asparagus in a shallow, heat-resistant, non-metallic baking dish and heat, uncovered, in Microwave Oven 1 to 2 minutes or until heated through. Arrange toasted English muffin halves on a heat-resistant, non-metallic serving platter. Place 1 slice of ham over 2 halves of the English muffin. Divide asparagus among the 4 muffins. Heat, uncovered, in Microwave Oven 2 1/2 to 3 minutes or until muffins and ham are heated through. Carefully place poached eggs on asparagus. Top with reserved sauce and heat, uncovered, in Microwave Oven 30 seconds to 1 minute or until hot.