1/2 c. plus 1 tsp. butter, softened and divided
3 1/2 c. powdered sugar
1/2 c. baking cocoa
1/4 tsp. salt
1/4 c. milk
1 tsp. vanilla extract
1 c. M&M'S® miniature baking bits

Line an 8-inch square pan with foil and grease the foil with 1 teaspoon butter; set aside. In a large bowl, combine the powdered sugar, cocoa and salt. Melt remaining butter; add milk and vanilla. Stir into sugar mixture and mix until smooth, then stir in the M&M'S®. Spread this mixture into the foil-lined pan and refrigerate until firm, at least 2 hours. Lift foil out of pan. Cut fudge into 1-inch squares. Store in airtight container in the refrigerator.