Note - Bake the cake and cool before starting the caramel mousse
Preheat oven to 350℉ (180℃)
Prepare a 9" cake pan by lining the bottom with parchment paper or greasing the pan.
Combine cocoa powder, flour, sugar, cornstarch, baking powder and baking soda in the bowl of a stand mixer. If mixing by hand or with a hand mixer, combine ingredients in a large mixing bowl.
⅓ Cup Cocoa Powder, 1 Cup All-Purpose Flour, 1 Cup Granulated Sugar, 1 tablespoon Corn Starch, 1 teaspoon Baking Powder, ½ teaspoon Baking Soda
Add oil and eggs and mix until combined.
2 Large Eggs, ⅓ Cup Vegetable or Canola Oil
Slowly pour brewed coffee into bowl while continuing to mix, scraping the bowl occasionally. The batter should be smooth.
⅔ Cup Brewed Coffee, cooled
Bake for 28 - 30 minutes, or until a toothpick inserted in the center of the cake comes out clean.
Place cake on a rack and allow to cool completely.
Remove cake from pan after cooling. Slice the dome off the cake to create a flat surface.
Simple Syrup
Combine granulated sugar and water in a saucepan. Heat over medium heat until sugar is dissolved and the water is just beginning to boil. Set aside to cool.
1 Cup Granulated Sugar, 1 Cup Water
Caramel Mousse
Sprinkle powdered gelatin over cold water. Set aside.
2 teaspoons Powdered Gelatin, 2 Tablespoons Cold Water
Lightly whip egg yolks in a bowl, set aside.
3 Large Egg Yolks
Place granulated sugar in a heavy-bottomed sauce pan.
½ Cup Granulated Sugar
Begin heating the sugar on medium heat and allow to come to a boil. Do not stir sugar.
Continue boiling sugar until it turns an amber color.
Turn heat to low and add butter and heavy cream. Use caution as the mixture may sputter. Stir until butter is melted. Note: the sauce may start to separate - just continue to stir until it comes together.
½ Cup Heavy Whipping Cream, 3 Tablespoons Unsalted Butter
Remove from heat and add white chocolate and gelatin. Stir until melted.
6 Ounces White Chocolate
Temper the egg yolks by slowly pouring ¼ of the caramel sauce into the eggs, whisking constantly to prevent eggs from curdling.
Place sauce pan on stovetop over low heat. Whisking constantly, pour the tempered eggs gradually into the saucepan. Whisk vigorously until the mixture thickens slightly and reaches 160℉ (71℃).
Pour mixture into a large bowl and set aside to allow to cool completely (approximately 30 minutes).
Begin whipping heaving cream (measure #2) to medium peaks. Medium whipped cream peaks hold their shape well but the tips curl over slightly when you lift the whisk.
1 ½ Cups Heavy Whipping Cream
Gently fold the whipped cream into the caramel mixture until it's fully blended and no white streaks are visible. Be careful not to fold to much, or you’ll lose the light, fluffy texture.
Assembling the Cake
Place cake layer in the center of springform pan. Poke about 20 holes in the chocolate cake with a dinner fork. Evenly brush the cooled simple syrup over the cake.
Pour caramel mousse over chocolate cake in the springform pan. Smooth the top with an offset spatula. Tap gently on the counter to release any air bubbles.
Place cake in refrigerator for 2 hours or until mousse is fully set.
Unmold the Cake
Dip a knife or offset spatula into a cup of hot water and run the knife around the inside of the springform pan. Gently release the spring on the pan. Place cake on a wire rack and prepare chocolate glaze.
Chocolate Glaze
Place chocolate, butter, corn syrup and water in a heat-proof bowl. Heat in the microwave for 30 second bursts at 50% power until melted. Stir between each heating. Alternatively, heat over a pot with simmering water and stir often (note: bottom of bowl should not touch the water).
8 Ounces Semi-sweet chocolate, 2 Tablespoons Light corn syrup, 1 Tablespoon Water, ¾ Cup Unsalted butter, room temperature
Allow glaze to cool slightly (5 - 10 minutes). Pour glaze over top of cake. Push glaze down the sides of the cake using an offset spatula.
Allow glaze to set and move to a serving platter.
Notes
Use caution when making the caramel. Hot sugar can may cause burns if it comes in contact with skin.