Makes about 2½ cups.
• 4 egg yolks
• 1¼ cups sugar
• 3 Tbs. unsweetened powdered cocoa
• ⅔ cup milk
• ½ lb. soft butter
1. Beat the egg yolks until they are creamy, then beat in ¾ cup of the sugar and continue until pale and fluffy. Beat in the cocoa.
2. Bring the milk to a boil and add it to the egg yolk mixture, a little at a time, while continually beating. When all the milk has been added, transfer the custard to a heavy-bottomed saucepan and stir it with a wooden spoon over very low heat until it thickens enough to heavily coat the spoon. Don’t even let it simmer.
3. When the custard has thickened, return it to the mixing bowl and set inside a larger one ½ full of cold water. Beat the custard until cool.
4. In another bowl, beat the soft butter with the remaining ½ cup sugar until it is fluffy. Add the chocolate custard and beat the two together until they are one perfectly smooth, creamy mixture. Chill the buttercream for about ½ hour before using it.