For the Red Velvet Cupcakes:
1. Preheat convection oven to 325 degrees. Prep baking rounds (I usually do a light coat of shortening and a dust of flour). Set aside.
2. In a large bowl, whisk together the eggs, buttermilk, sour cream, vegetable oil, and vanilla until thoroughly combined.
3. Sift in cake mix and stir until just combined. Will be thick.
4. Divide batter evenly into cake rounds. Bake for 25-27 minutes, depending on your oven, until centers have cooked through and spring back when touched.
5. Remove rounds from oven, and let cool in pans for 2 minutes, then turn over onto a wire rack to cool (I usually wrap mine in plastic wrap when they are barely room temperature, freeze for at least 30 minutes to overnight before frosting).
For the Buttercream:
1. In the bowl of a stand mixer fitted with a paddle attachment, whip up the butter on high until light and fluffy.
2. Add in hot chocolate mix, cocoa, salt, vanilla, and heavy cream. Add in tablespoons of pudding mix, if using.
3. Slowly add in the powdered sugar with the mixer on low speed about ½ cup at a time. Add in more heavy cream or more powdered sugar to achieve desired consistency.
4. Turn up the speed to high for about 2-3 minutes until it's very light and fluffy, then turn the speed down to low for about 30 seconds to beat out any air bubbles. Continue the beating with a wooden spoon if needed.
For the Toasted Marshmallow Filling:
1. Preheat oven to 350 degrees and prep a baking sheet with parchment paper.
2. Place about 2-3 cups of marshmallows (not the jumbo size ones) on prepared baking sheet. Bake for 5-7 minutes, or until the marshmallows have expanded and are toasted brown on top. Remove from the oven and set aside.
For the Chocolate Ganache Drip:
1. In a medium glass bowl, stir together the chocolate and heavy cream. Microwave for 30 seconds, then stir with a small whisk until chocolate ganache has zero lumps and is smooth. Add to a squeeze bottle for ganache drip. Set aside.
1. Tape 8" cardboard cake round to a 6" cake round. Place the cake rounds on a cake turntable.
2. Using an angled icing spatula, place on a bit of the buttercream to act as glue for the first cake round.
3. Place on the first cake round, add on a little layer of buttercream, then pipe a dam around the outside ring of the top of the cake round. Hand place on a few of the toasted marshmallows until it fills the center. Place the next cake rounds on top and repeat.
4. Crumb coat and freeze for 10 minutes.
5. Final coat then freeze for 10 minutes.
6. Add on the ganache drip, then freeze for 3 minutes to set the ganache, then top with marshmallows.