Best Ever Butter Cream Frosting

1 Heat milk to boiling, and then let cool. In a large bowl, beat egg white until stiff. Add sugar, butter, and vanilla. Mix with mixer till well blended. Add cooled milk, then beat until nice and creamy. Will take about 15 to 20 minutes of beating after adding the milk. Use to frost any kind of cake. Best if kept refrigerated after frosting cake.