Prepare the mousse at least four hours or up to two days in advance. Refrigerate, covered with plastic wrap.

　　

Ingredients

makes enough for one 18-inch roulade

　　1 1/2 cups heavy cream

　　6 ounces best-quality bittersweet chocolate, finely chopped

　　2 tablespoons instant espresso powder

　　2 tablespoons boiling water

　　1/4 cup sugar

　　2 tablespoons light corn syrup

　　4 large egg yolks

　　

Step 1

In the bowl of an electric mixer fitted with the whisk attachment, whip the cream to soft peaks; cover with plastic wrap and refrigerate. In a heatproof bowl set over (but not touching) simmering water, melt the chocolate. Remove from heat. In a small bowl, stir the espresso powder into the hot water until dissolved.

　　

Step 2

In a small saucepan, bring the sugar, corn syrup, and 1 tablespoon water to a boil over medium heat, and cook until mixture registers 238°F on a candy thermometer, about 3 minutes; remove from heat.

　　

Step 3

In the bowl of an electric mixer fitted with the whisk attachment, beat the yolks on medium speed until lightened, about 3 minutes, scraping down the sides of the bowl as needed. With the mixer on medium speed, gradually pour the sugar syrup down the side of the bowl in a slow, steady stream. With the mixer on high speed, beat until the mixture holds a ribbon-like trail on the surface for 2 seconds when the whisk is raised, about 2 minutes more. Beat in the melted chocolate and the espresso mixture to combine. Using a rubber spatula, gently fold in the chilled whipped cream until there are no streaks and the mixture is well combined.

　　Reprinted with permission from Martha Stewart's Baking Handbook by Martha Stewart. © 2005 Clarkson Potter