Preheat the oven to 325 degrees. Grease and flour three 8” baking pans (alternatively line with parchment, making sure to grease the sides of the pans).

Start by browning the butter. In a medium sauce pan, melt butter over low heat, stirring frequently. The butter will eventually begin to foam. Once the foam subsides, continue to stir until specks of brown begin to form in the butter, and the butter begins to smell slightly nutty. Remove from heat and set aside.

In the bowl of a stand mixer, beat the eggs and the brown sugar for 3-4 minutes until thick (alternatively use a large mixing bowl and electric beaters). Add in the coffee, bourbon and sour cream and mix until thoroughly combined. Add in the browned butter and vanilla, mixing well.

Sift in the flour, cocoa powder, salt, baking soda and baking powder. Mix until just combined. Fold in the chopped chocolate.

To make the mousse, combine the egg yolks, sugar and vanilla in a large saucepan. Mix in half of the whipping cream. Heat over low heat, stirring until mixture just begins to bubble around the edges. Add in chopped chocolate and mix until incorporated. Set aside.

Once the mixture boils, remove from heat and add in the gelatin, mixing gently. Strain mixture into a shallow bowl and cover with plastic wrap, making sure the wrap in placed directly onto the surface of the mixture. Set aside for approximately two hours until mixture has cooled to 90 degrees.

To assemble, spread mousse between layers of cake. Frost top and sides of cake with mousse, smoothing out as much as possible so mirror glaze will have a flat, even surface.

Once mirror glaze has cooled, strain into a jar or container with a spout. Set cake on wire rack over a lipped baking sheet, and pour the glaze over the top, using a continuous motion and making sure to get the edges. Once the cake has been covered, transfer back to your serving platter using a cake lifter or two off-set spatulas.