In a medium-sized, heat-resistant, non-metallic bowl melt the 1/2 cup butter in Microwave Oven 1 minute.
Add onion, celery and mushrooms and heat, uncovered, in Microwave Oven 5 minutes or until vegetables are tender.
Sprinkle sage over vegetable mixture.
Add chicken broth and stir to combine.
Heat, uncovered, in Microwave Oven 3 minutes.
Add bread stuffing and toss lightly.
Lightly grease 8 small, heat-resistant, non-metallic custard or coffee cups with butter.
Divide stuffing among cups.
Just before serving, heat, uncovered, in Microwave Oven 8 minutes or until heated through.