This frosting has a light, appealing mousselike texture. Try it between layers of any angel cake, a moist sponge cake, or a devil’s food cake.
Whisk together in a medium heatproof, preferably stainless-steel, bowl:
      2 large eggs
      2 cups powdered sugar
      1/2 cup milk, strong coffee, or water
      1/8 teaspoon salt
Set the bowl in a large skillet of barely simmering water and heat, stirring constantly, until the mixture registers 160°F on an instant-read thermometer. Remove from the heat and stir in:
      4 ounces unsweetened chocolate, finely chopped
      6 tablespoons unsalted butter, cut into small pieces
      1 teaspoon vanilla
Stir until the chocolate and butter are melted and the mixture is smooth. Set the bowl in a larger bowl of ice water and beat on high speed until the frosting holds a shape. Use immediately or refrigerate for up to 4 days. Soften and beat until smooth before using.