Preheat the oven to 325 degrees F. Spray two 8-inch round cake pans with non-stick spray, line with parchment paper, and spray again. Set aside.

Combine the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined.

In another bowl, whisk together the buttermilk, water (or coffee), oil, eggs, and vanilla.

With the mixer on low speed, slowly add the wet ingredients to the dry, scraping the bottom of the bowl with a rubber spatula.

Divide the batter between the two pans and bake for 30 to 35 minutes, or until a toothpick inserted in the center of the cake comes out with a few moist crumbs on it.

Cool in the pans for 10 minutes, then turn them out onto a cooling rack and cool completely.

Torte each cake layer, dividing it in half horizontally. Wrap each cake (the two thin layers for each cake can be wrapped together) and freeze until ready to use.

Preheat the oven to 325°F. Line a cookie sheet with parchment paper. Set aside.

Combine the graham cracker crumbs, brown sugar and flour in a medium-size mixing bowl. Whisk to combine.

Stir in the melted butter, making sure all the crumbs get coated and form clusters.

Spread the clusters on the prepared sheet pan. Bake for 7 minutes and then toss the crumbs a bit and bake for another 7 minutes.

Allow the clusters to cool completely on the pan before using. The clusters can be stored in an airtight container at room temperature for 1 week, or in the refrigerator or freezer for up to 1 month.

In a medium size mixing bowl (ideally a chilled stainless steel bowl), combine the ingredients. Beat on high speed until medium-stiff peaks form.

Store in an airtight container in the fridge until ready to use. Can be made a day ahead.

In a small mixing bowl, combine the crumbs with the heavy cream. Stir to combine. Allow to rest for about 10 to 20 minutes. The mixture should be thick, like a paste. You can use this right away or store in the fridge until ready to make the rest of the buttercream.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until light and fluffy, about 2 minutes.

Add the graham cracker paste and continue to mix on medium-high for another minute or two. The mixture should be smooth and silky.

With the mixer on low speed, gradually add the powdered sugar, followed by the cinnamon, vanilla and salt. Make sure to scrape down the sides and bottom of the bowl.

Turn the mixer to medium-high speed and beat the buttercream for an additional 3 to 5 minutes. The buttercream should be lighter in color and fluffy and smooth in texture.

In a microwave save bowl, combine the chocolate chips and the heavy whipping cream. Heat for about 30 seconds and then stir. Continue to heat in 30 second increments until the chocolate is melted and smooth.

The mixture should be thin enough to drip around the top of the cake. If it’s too thick, add a few more tablespoons of warm heavy cream. If it’s too thin, add more chocolate chips.

On a cake board or cake stand, place the first layer of cake (this should be one of the bottom pieces of the torted cake). Pipe a rim of buttercream around the top edge of the cake.

Evenly spread half of the chocolate mousse filling on the cake layer, Top generously with an even layer of graham cracker clusters, gently patting them in place.

Place the next cake layer (this will be the top half of the cake) on the filling. Evenly spread about 1 cup of buttercream over the cake. Again, generously top with an even layer of clusters, gently patting into place.

Place the third cake layer (this should be the top half of the second cake layer) on the filling.

Pipe a rim of buttercream around the top edge of the cake. Fill with the second half of the mousse and again top with clusters.

Place the final cake layer (the bottom half of the second cake layer) on the filling (bottom side up).

Evenly spread a thin layer of buttercream around the entire cake to create the crumb coat. Freeze the cake for 15 minutes.

Continue to frost the cake with the remaining buttercream and apply the drip.