Line two 8-inch by 2-inch round cake pans with plastic wrap. Spray with non-stick cooking spray and set aside.

Place 1/2 cup of the water in the bowl of a stand mixer fitted with the whisk attachment. Sprinkle the gelatin on top of the water. Let it soak without stirring.

Meanwhile, combine the remaining 1/4 cup water, corn syrup and sugar in a medium size saucepan over medium heat.

Bring the mixture to a boil and let it boil for about a minute.

Turn the heat off. With the mixer on medium speed, carefully and slowly pour the hot sugar mixture into the gelatin mixture. Add the vanilla.

Continue to beat the mixture on high for 10 to 12 minutes. The mixture should look fluffy and reach stiff peaks.

Spray two more pieces of plastic wrap with non-stick spray and then place one piece of plastic wrap on each of the marshmallow layers, pressing down lightly to seal the candy.

Allow the marshmallow candy to rest overnight.

Using a shallow dish, evenly spread the powdered sugar over the dish and then dip each marshmallow layer in the powdered sugar (top and bottom).

Preheat your oven to 325 degrees F. Spray three 8-inch round pans with nonstick spray, line the bottom with parchment paper and spray again. Set aside.

In a medium bowl, whisk together flour, salt, and cocoa powder. Set aside.

In the bowl of an electric mixer, fitted with the paddle attachment, combine the butter and sugar. Beat on medium speed until light and fluffy, about 2 minutes. Scrape down the sides of the bowl and mix again for another minute.

Add the eggs, one at a time, being sure to mix and scrape down the sides of the bowl between each addition. Once all of the eggs are added, continue to beat on medium-high speed for about two minutes, until the mixture gets lighter in color and bigger in volume.

With the mixer on low speed, add 1/3 of the flour mixture, followed by 1 cup of the buttermilk. Continue with another 1/3 of the flour, the second half of the buttermilk and then the remaining flour mixture. Stir until combined.

In a small bowl, combine the vinegar and baking soda. The mixture will bubble. Add the mixture to the cake batter and stir on low until combined. Scrape down the sides of the bowl and mix again for another 20 seconds.

Fold in the sour cream until no streaks remain.

Mix the sugar, water and corn syrup in a small saucepan over medium heat.

Bring the mixture to boil, but DO NOT STIR! (Stirring encourages crystallization). Let the mixture cook until it turns to a golden brown/amber color. It happens quickly, so keep an eye on it.

Remove the caramelized sugar syrup from the heat and very slowly stir in the cream, pouring it in little by little, to temper the cream and sugar syrup. If you pour it in all at once, your sugar will turn into hard candy. You can start adding more and more as you go along.

Heat the cream and chocolate chips together in the microwave for about 45 to 60 seconds. Stir the mixture until the chips are melted. If the chocolate isn't melting enough, heat the mixture again for another 30 seconds. Stir until smooth. Set aside to cool. We want the ganache to be close to room temperature before adding it to the butter.

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

With the mixer on medium speed, gradually add the ganache mixture, scraping down the sides and bottom of the bowl as needed. Beat until silky, smooth.

With the mixer on low speed, gradually add the powdered sugar, followed but the vanilla and salt. Turn the mixer to medium-high and beat the buttercream for about 3 to 5 minutes.

Place the first cake layer top side up, in the center of the cake board. Spread about 2/3-3/4 cup of the chocolate buttercream on top of the cake layer with an offset icing spatula.

Place one of the marshmallow layers on top of the buttercream and then pipe a rim of buttercream around the edge of the marshmallow.

Gently spread 1/3 cup of the caramel over the cake marshmallow.

Repeat for second cake layer.

Place the final cake layer, top side down, on the second layer of filling.

Apply a thin layer of buttercream around the cake. Freeze the cake for 15 minutes to set the crumb coat.

Once the crumb coat is set, continue frosting the cake with the remaining buttercream. Top with remaining caramel.