Chocolate and mint have a natural affinity for each other, so combining layers of sweet chocolate cake with mellow mint cream mousse is a natural combination too. Add in soft swirls of semi-sweet ganache, chill well and you've got a cool and creamy dessert that is very refreshing.
Preheat the oven to 350°F. Prepare a 10" x 15" jelly roll pan by lining with parchment and spritzing with cooking spray.
For the cake batter: In a stand mixer whip the eggs until thick and pale yellow. Gradually beat in the sugar, salt, and vanilla.
Sift together the flour, cocoa, and baking powder. Fold into the thick egg mixture.
In a measuring cup, whisk together the oil and buttermilk. Fold into the chocolate batter until just combined.
Pour the cake batter into the prepared pan and bake for 8 to 12 minutes. The edges will begin to pull away from the sides of the pan and the center will spring back when lightly pressed.
Remove the cake from the oven and use a knife to loosen the edges. Lift the cake and parchment paper onto a rack to cool.
To prepare the mint filling: In a small bowl stir together the sugar and Instant ClearJel. In a large bowl, mix the cream, peppermint oil and green food coloring.
Whip the cream until it begins to thicken. Sprinkle in the sugar mixture and continue whipping until the mixture is quite thick and mousse-like.
To prepare the ganache: Place the chopped chocolate in a heat-proof bowl. Add the heavy cream and microwave for 60 to 90 seconds, or until the cream is very hot. Whisk together the mixture until the chocolate melts and the ganache is smooth. Place in the freezer for 20 minutes, to cool and thicken.
To assemble the cake: Cut the cooled cake crosswise into four even sections, each a scant 4" x 10". Spread three of the sections with 1/4th of the cooled, thickened ganache. Reserve the last 1/4th of ganache for serving.
Divide the filling into thirds. Spread or pipe 1/3 of the filling onto each ganache-topped cake section. Be sure to leave one cake section unfilled, to place on top.
Carefully stack the three filled sections. Place the fourth (unfilled) section on top, pressing down on the whole stack gently.
Wrap the whole torte firmly in plastic wrap. Freeze at least 2 hours, or up to 2 days. Remove from the freezer, remove the plastic wrap, and let the cake thaw for about 15 minutes before serving. Reheat the reserved ganache, and pour it over the cake before slicing. Serve cold.
1/2 teaspoon of peppermint extract can replace the peppermint oil in the recipe. Adjust to taste. Pale pink coloring would also work nicely with the mint flavoring.
