Prepare a 9" cake pan by lining the bottom with parchment paper or greasing the pan.
Combine flour, sugar, cornstarch, salt, 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.
Add oil and eggs and mix until combined.
Slowly pour brewed coffee into bowl while continuing to mix, scraping the bowl occasionally. The batter should be smooth.
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.
Make the Caramel Mousse
Sprinkle powdered gelatin over cold water. Set aside.
Lightly whip egg yolks in a bowl, set aside.
Place granulated sugar in a heavy-bottomed sauce pan.
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 (measure #1). 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.
Remove from heat and add white chocolate and gelatin. Stir until melted.
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° F.
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.
Gently fold into caramel mixture.
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.
Assembling the Cake
Place cake layer in a 10" springform pan. Poke 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).
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.