A few weeks ago I thought about making these coffee chocolate towers for the HHDD mousse event, but I ended up making the chocolate peanut butter mousse cake instead. But these towers of mousse from Emily Luchetti's "A Passion for Desserts" looked too good not to try. And what's not to like about chocolate cake with white chocolate coffee mousse?
In my humble, non pastry professional opinion I'll admit that the chocolate cake base didn't really add much to this dessert. But I'm not one to question Emily Luchetti's expertise. But just between you and me, the star is really that column of mousse.
Since the mousse is essentially just heavy cream and white chocolate, try to use the best ingredients you can find. I used heavy cream from the Strauss Family Creamery in nearby Tomales Bay and white chocolate (31% cocoa butter content) from E. Guittard. Don't use that "white colored chocolate" which is made from solid or hydrogenated vegetable fats. Make sure there is actually cocoa butter in your white chocolate. It'll really make a difference in the finished mousse.
Coffee Chocolate Towers
1/4 cup cocoa powder
6 tbsp all purpose flour
1/8 tsp baking powder
pinch of salt
2 ounces (4 tbsp) unsalted butter, softened at room temp.
1/2 cup granulated sugar
2 large eggs
3 tbsp buttermilk
1/2 tsp vanilla extract
White Chocolate Coffee Mousse
9 ounces high quality white chocolate
1/4 cup strong coffee
2 tsp instant espresso powder
1 1/4 cup heavy whipping cream
3/4 cup heavy whipping cream
1 tbsp light corn syrup
1 ounce (2 tbsp) unsalted butter
8 ounces bittersweet chocolate, finely chopped
To make the chocolate cake
Preheat oven to 350F. Butter and 8-inch square pan and line with parchment paper. Butter the paper.
Sift together the cocoa, flour, baking powder, and salt. Set aside dry ingredients.
Cream butter and sugar until smooth, about 1 minute with a stand mixer. Add the eggs, one at a time, beating for 15 seconds after each addition.
In a small bowl, stir together the buttermilk and vanilla. On low speed, add the dry ingredients in 3 additions alternating with the buttermilk and ending with the dry ingredients, mixing until just combined. Evenly spread batter into prepared pan.
Bake at 350F for about 15 minutes or until cake tester comes out clean. Let cake cool in pan.
According to Emily, if you don't have pastry ring molds for your mousse towers, you can use 6-ounce tomato paste cans. Just cut off both ends and you'll have reusable ring molds. Or, if you don't have tomato paste cans, you can use stainless steel cookie cutters like I did.
To cut the chocolate cake
Run a knife around the inside edge of cake pan and invert onto a cutting board. Peel off parchment paper. Using a clean pastry ring mold or tomato paste can (see note), cut out 6 circles of cake. Set cake circles aside.
Line the insides of six 6-ounce tomato paste cans (see note) with pieces of parchment paper 7.5 x 3.5 inches long, Place the lined cans on a parchment lined baking sheet.
To make the mousse
Melt the white chocolate, coffee, espresso powder together in a medium bowl set over a pot of barely simmering water. Whisk until smooth and let cool to room temperature, stirring occasionally.
In a large bowl, whip the cream until very soft peaks form. Fold the white chocolate mixture into the cream. Divide the coffee cream between the lined tomato paste cans (see note).
To make the glaze
Warm cream, corn syrup, and butter in a medium saucepan over medium heat until it bubbles around the edges. Remove from heat and whisk in the bittersweet chocolate. Cool until glaze has thickened but is still pourable, about 15 minutes.
Place a chocolate cake circle gently but firmly in each can on top of the mousse. Remove the mousses from the cans and place them cake side down onto wire rack. Peel off the parchment paper. Place the rack on a sheet pan line with parchment paper. Carefully pour the glaze over the top of each of the mousses, letting it run down the sides. Refrigerate towers until firm, about 1 hour.
The towers can be made one day in advance and kept refrigerated.