Preheat the oven to 350 degrees Fahrenheit.
Line two round 8 inch cake pans with parchment paper and set aside. See notes about using 9 inch pans.
Combine the room temperature milk with the vinegar and mix together in a glass. Set aside.
In a large mixing bowl (mixing is easier if the bowl is extra large!), sift together the almond flour, all purpose flour and cocoa powder. Whisk in the remaining dry ingredients. The espresso powder is optional, but it really enhances the chocolate flavor. I promise it won't taste like coffee at all!
Add in all remaining wet ingredients and whisk together until smooth.
Add the batter to the prepared cake pans, trying to keep them as even as possible to ensure even baking.
Let sit for 5 minutes.
Add to the oven and bake for 34-42 minutes or until an inserted toothpick comes out with a few crumbs. You don't want to underbake since the cake will sink in the middle or end up dense, but over-baking will lead to a dry cake, so start your timer at 34 minutes, and add just a couple of minutes at a time until the toothpick has a few crumbs but isn't wet.
Remove from the oven and let cool in the cake pans for 30 minutes.
Carefully flip onto a cooling rack and let cool completely before frosting. I usually stick them in the fridge to cool, which takes about 90 minutes.
Prepare the vegan buttercream, then frost the top of one layer, add on the second layer, then frost the top and sides of the cake.