Microwave Fudge

1 16 ounce package powdered sugar, sifted
1/2 cup cocoa
1/4 teaspoon salt
1/2 cup butter or margarine
1/4 cup milk
1 tablespoon vanilla extract

combine first 3 ingredients in a 2-quart glass bowl; add butter.  Microwave at
HIGH, uncovered, 2 to 3 min.; add milk, stirring until blended.  Microwave at
HIGH 1 min.  Stir in vanilla; pour into a lightly greased 8-inch square pan. 
Refrigerate until fudge is firm; cut into squares.  Yield; 1 1/2 pounds