Preheat the oven to 325 degrees F. Grease two 9-inch round cake pans and line the bottoms with parchment paper.
Place the chopped chocolate in a medium bowl and pour in hot brewed coffee. Stir until the chocolate is melted. Set the mixture aside.
In a large bowl, sift together sugar, flour, cocoa powder, baking soda, baking powder, and salt. Mix well with a whisk.
In the bowl of a mixer (or just a large bowl if using a hand mixer), beat eggs until they thicken slightly, about 3 minutes. Gradually mix in canola oil, buttermilk, vanilla, and chocolate/coffee mixture until the mixture is well combined.
Gradually add the sugar mixture, and beat on low speed until combined. Avoid beating on medium or high speed so that there is not too much air in the batter. Do not overmix or the cake will become tough.
Pour the batter into the prepared pans and bake until a tested inserted in the center comes out clean, about 50 to 65 minutes. Place the pans on a rack and let the cakes cool in the pans for 20-30 minutes. Once cool, invert the cakes onto the rack. Carefully remove the parchment paper.
I recommend making the cake layers earlier in the day or the day before. Once the layers are completely cool, wrap well in plastic wrap and refrigerate. If you have the opportunity, freeze the layers for about 1 hour. This will allow the cake to become slightly firm, which will make the layers much easier to split later.