1 stick (4 ounces) unsalted butter, cut into pieces
1 cup confectioners' sugar
3 tablespoons amaretto
2 egg yolks
In a medium bowl set over a small saucepan of simmering water or in the top of a double boiler, melt the butter. Slowly whisk in the sugar until the mixture is creamy, about 30 seconds. Add the amaretto and then the egg yolks, 1 at a time, whisking constantly. Cook, whisking constantly until the sauce is the consistency of honey and reaches 160°, about 4 minutes. Let cool to room temperature
The sauce can be covered and refrigerated overnight. Let return to room temperature before using.