Preheat the oven to 350 degrees F and line a 9" square pan with parchment paper.

Soak cake strips in ice water.

In a medium bowl, whisk together the flour, sugar, cocoa powders, baking powder, and salt. Set aside.

In a large bowl, whisk together the milk, oil, eggs, and vanilla.

Add the dry ingredients to the wet and whisk until just combined.

Lastly, whisk in the hot coffee until fully combined.

Pour the cake batter into the prepared pan and wrap the soaked cake strips around the outside of the pan. Bake for about 25 minutes or until a toothpick inserted comes out clean the cake pulls away from the sides of the pan.

Allow the cake to cool in the pan completely. Cover with plastic wrap and set aside until ready to assemble.

In a medium bowl, add the chocolate and set aside.

In a small saucepan, bring 170g (¾ cup) heavy cream to a simmer (or about 190 degrees F), then pour over the chocolate and mix until smooth.

Whisk in the egg, vanilla, and salt until fully combined.

In a separate small bowl, add the remaining 113g (½ cup) heavy cream and use an electric mixer to beat until stiff peaks form.

Add the whipped cream to the chocolate mixture and gently fold with a rubber spatula until fully combined.

Pour into a shallow dish and press plastic wrap up against the surface and chill for at least one hour.

Line a pullman pan with parchment paper.

Cut the cooled cake in half, and each half into two layers, giving 4 layers measuring roughly 9x5. You may need to trim the sides to make them fit in the pan.

Add the first cake layer to the bottom of the pan and top with ⅓ of the mousse. I used a 3 tbsp cookie scoop and added 4 scoops to each layer.

Repeat with the remaining cake layers and mousse. Set aside.

In a small saucepan, bring the heavy cream to a simmer (or about 190 degrees F), then remove from heat, add the chocolate, and mix until smooth.

Pour the warm ganache over the assembled cake and spread into an even layer.

Place the cake in the fridge uncovered and chill for at least two hours before serving.