Preheat oven to 350 F. Grease a 9x13 inch baking pan and set aside.
In a large bowl, stir together the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Set aside.
In a separate bowl, whisk together the buttermilk, melted butter, eggs, and vanilla until smooth.
Pour the wet ingredient mixture into the dry ingredient mixture and stir until combined.
Add the hot coffee
Mix until the batter is smooth
Transfer the cake batter into the prepared baking pan. Bake for 30-35 minutes, or until a toothpick or sharp knife inserted into the center comes out clean.
When the cake is finished baking, remove it from the oven. While cake is still warm, poke holes all over the surface of the cake using a clean utensil, such as the back of a wooden spoon.
Pour the condensed milk and caramel sauce over the surface of the cake.
Allow the cake to cool and then chill in fridge for at least an hour
To prepare the whipped topping: In a stand mixer, whip together the heavy cream and powdered sugar until stiff peaks form.