In another large bowl add the oil, eggs, sour cream and buttermilk. Mix until smooth and well combined. Alternate mixing the dry ingredients into the wet with the hot coffee (dry, coffee dry, coffee dry) until smooth and well combined.
Evenly pour the chocolate cake batter into each of the prepared cake pans. Bake the chocolate cakes for about 35 - 40 minutes. Cool the cakes in the pan for 15 minutes then carefully remove the cakes from the pan to cool completely.
Make the chocolate buttercream frosting. Beat the butter on medium speed until smooth and creamy. Mix in the cocoa powder, powdered sugar, vanilla extract, 3 tablespons (45 ml) milk and salt on low until mostly combined.
Smear a small amount of frosting onto the serving plate or cake stand. Place the first chocolate cake layer on top. Apply a layer of frosting to the first layer of cake. Repeat with the next two layers of chocolate cake. Place the cake in the fridge to set for about 20 - 30 minutes. Apply the rest of the frosting to the cake and return to the fridge for another 20 minutes.
Make the ganache. Pour the warm ganache over the cold and frosted chocolate cake, gently allowing the ganache to pour over the sides into a drip or to smooth into another layer of chocolate icing. Top with chocolate chips, slice and serve.