For the cake, put flour, sugar, cocoa, baking powder, baking soda and salt in a bowl and mix well.
In a stand mixer, mix the buttermilk, oil, eggs, vanilla together. Slowly add in the mix of dry ingredients while the mixer is on low. Add the coffee and make sure everything is combined. The batter will be very thin.
Pour the batter into the prepared pan and bake for about 30-35 minutes or until the center of the cake springs back when you touch it.
While the cake is still warm, poke lots of holes all over the cake with a small skewer or a fork.
Make the filling:
Whisk sweetened condensed milk, half-and-half, evaporated milk, and 3 tablespoons cocoa powder together in a bowl. The cocoa may not completely dissolve, but whisk until it is mostly incorporated.
Slowly pour the milk mixture evenly over the warm cake.
Allow the cake to cool completely.
Make the Whipped Cream Topping:
*Refrigerate the bowl of a stand mixer for 10 minutes to get it cold.*
Sift the powdered sugar and cocoa powder together.
Beat the cold heavy cream in the cold stand mixer bowl using the whisk attachment for 1 minute.
Add half of the sugar/cocoa powder mixture. Beat until it is fully mixed in, then add the remaining sugar mixture.
Continue to beat until soft peaks form and the mixture is spreadable. It should be fluffy and light.
Assemble the cake:
Spread the chocolate whipped cream on the cooled cake.
Drizzle with chocolate syrup or sprinkle with mini chocolate chips.
Store in an airtight container in the refrigerator.
The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**