• Preheat the oven to 180 (350f) and prep two 8-inch baking pans with cooking spray and parchment paper.
• Into a large mixing bowl, add the dry ingredients: flour, granulated sugar, kosher salt, baking powder, and baking soda, sift the cocoa powder, and mix with a whisk.
• Add the buttermilk, vegetable oil, vanilla extract, and eggs, and mix until almost combined.
• Add the hot coffee and mix until just combined and there are no lumps of flour visible. The batter should be pretty runny and smooth.
• Divide the mixture into two 8-inch baking pans, I suggest using cake strips for even baking. (weight the batter for better results) and bake in a preheated oven for 25-30 minutes or until a toothpick comes out clean. (You can also use a 9-inch cake pan)
• Let the cake cool completely before frosting so the frosting won't melt off the cake.

Make the cream filling:

• Into a saucepan, add the flour, and sugar, and mix with a whisk until well combined.
• Add the milk and heat it over medium heat until the mixture simmers mixing constantly. After two minutes of the simmering mixture, it should thicken up. Remove it from the heat.
• Pour the milk mixture into a large baking pan and cover it with plastic wrap to prevent skin from forming. You will need to let the mixture cool completely so it wouldn't melt the butter.
• Let the milk mixture chill in the fridge for at least an hour or 30 minutes in the freezer.
• Into a large mixing bowl, add the softened butter and vanilla extract and whip with an electric hand mixer or stand mixer with the balloon attachment for 2-3 minutes until smooth and fluffy.
• Add the cooled milk mixture and whip it for another 3-5 minutes over high speed. The filling should look similar to whipped cream.

Make the chocolate ganache

• Melt dark chocolate and heavy cream in a small to medium mixing bowl in the microwave for about 1 minute.
• Let the chocolate and the cream sit for 10 minutes for the chocolate to melt, then mix until the chocolate ganache is smooth and silky.

Assemble the cake

• Pipe a small dollop of the frosting on the surface that you will frost on. Lay the first cake layer over the frosting dot.
• Top the first cake layer with the cream filling and spread an even layer using a spatula.
• Top with the second cake layer and smooth out the sides.
• Top the cake with the chocolate ganache and smooth it out using an offset spatula making sure the entire cake is coated.