Combine butter, milk
, corn syrup, and vanilla in medium saucepan
and heat over medium heat until butter is melted. Decrease the heat to low, add the chocolate
, and whisk
until melted. Turn off heat, add the powdered sugar
, and whisk until smooth. Place the mixture over a bowl of warm water and dip the doughnuts
immediately. Allow glaze
to set for 30 minutes before serving.