For the Biscuit Roule (Jelly Roll/Yellow Cake):
1/2 cup flour
pinch of salt
4 eggs, separated
3/4 cup sugar
To make the cake: Preheat oven to 375 degrees. Grease a jelly roll baking sheet 15 by 10 inches. Line it with waxed or parchment paper. Butter the pan, then flour it. Tap it upside down to remove the excess flour. In a large bowl, beat the yolks with 1/2 cup sugar until light and thicken enough to leave a ribbon trail. Whip the egg whites until stiff but not dry. Add remaining 1/4 cup sugar and beat 30 seconds longer. Gently fold flour and whites into yolk mixture, alternating 1/3 cup of the flour with half the whites. Spread the batter evenly on prepared baking sheet. Bake 8 to 10 minutes, until edges are lightly browned. Place a smooth, cotton towel lightly dusted with sifted confectioners' sugar over the top and invert onto a rack to cool, remove paper.
Prepare ganache for filling and frosting:
1 cup heavy cream
12 ounces semi-sweet chocolate or bittersweet Callebaut
Scald the cream. Remove from heat. Add chopped chocolate. Stir until melted. Leave to cool; then beat for 5 minutes so the ganache is light and smooth.
For the Meringue Mushrooms:
3 egg whites
3/4 cup sugar
1/2 teaspoon vanilla
Turn oven down to 250 degrees. Butter and flour a baking sheet. Stiffly beat the egg whites, if possible using a copper bowl (copper gives a stiffer meringue). Beat in a tablespoon of sugar until whites are glossy, then fold in the remaining sugar with the vanilla. Place the meringue in a pastry bag fitted with 1/2 -inch tip. Pipe mounds of meringue for mushroom caps (smoothing any peaks) and strips for stems. Bake 15 minutes. Push stems into caps. Sprinkle with sugar and powdered cocoa. Bake another 30 minutes until dry and crisp.
To assemble: Spread 1/3 of the ganache on cake and roll using paper to help. Trim the edges of roll by cutting a diagonal 2-inch portion from each end; and reserve trimmings. Set trimmings on an angle on cake to form a branch. With remaining 2/3 of the ganache, frost, using fork tines to make bark on log. Fill in ends, covering completely. Cover the branch with ganache. Set the mushrooms around the log. Chill before serving.
Yield: 8-10 servings
For Chocolate Cake Yule Log: Add 6 tablespoons cocoa powder to flour in the biscuit roule portion and proceed with directions.
For a whipped cream filling: whip 8 ounces whipping cream, 1/2 teaspoon vanilla, and 1 to 3 tablespoons sifted confectioners' sugar until stiff. Spread on chocolate cake and proceed with rolling.