Microwave Fudge (Grandma Severson's Recipe)

2 packages powdered sugar (1 lb. each)
1 cup cocoa (unsweetened)
1/2 cup milk
1 cup butter
1 1/2 cup nuts (optional)
2 T. vanilla

Recipe is easily halved!  Mix sugar and cocoa in large microwave-able bowl.  Pour milk on top; do not stir.  Lay butter on top; do not stir.  Microwave on High 4 1/2 - 6 minutes, or until butter melts.  Add nuts/vanilla and beat with electric mixer until smooth.  Spread into well greased dish.  Chill; serve cool.