Chocolate Frosting (Satin)

It's a fluffy, light-chocolate frosting when whipped by mixer. For darker, glossier frosting, beat with spoon.

3 (1½ oz) squares unsweetened chocolate
3 cups confectioners' sugar, sifted
4½ Tbsp. hot water
1 egg
½ cup butter, softened
1½ tsp. pure vanilla extract

Melt chocolate in mixing bowl over hot water. Remove from heat. With electric mixer blend in sugar and water. Beat in egg, then butter and vanilla.

Frosting will be thin at this point, so place bowl in ice water; beat till of spreading consistency. Frosts tops and sides of two 9½" layers.