This is how you make Buttercream.

Prepare the equipment and the ingredients. The egg yolks with the whole eggs, the water with the sugar, the softened butter and the coffee extract. Bring the sugar and water to a boil in a heavy saucepan and skim the sugar. Boil without stiring, washing down any sugar crystals on side of the pan with a pastry brush dipped in cold water. Continue boiling until the syrup registers 118° to 120° celsius on a thermometer.

When it reaches this temperature remove from the heat. Beat the eggs in a large bowl. Add the hot syrup to the eggs in a slow stream and beat the mixture until completely cool. Gradually add the butter one piece at a time, beating well after each addition until incorporated. Continue beating until the buttercream is smooth. Add an extract of coffee to the taste and beat one more minute.

Use the buttercream immediately or cover and place in the refrigerator.