Start by making the buttercream. Cream the butter and Crisco until light and fluffy. Add in 1/2 of the powdered sugar and 1/2 of the cocoa powder. Mix on low speed until incorporated and then beat on high speed until creamy. Add in the rest of the powdered sugar and cocoa powder, the vanilla extract and half of the milk and heavy cream. Mix on low speed until incorporated. Add in more milk and heavy cream as needed, one tablespoon at a time. Beat on high speed until creamy and fluffy.
Remove the cakes from the freezer and unwrap them. Use a serrated knife to level out the cakes so that they're as flat as possible. Begin assembling the cake. Put one layer of cake on a cake board and spread 1 cup of frosting on top. Don't worry if it hangs over the edges of the cake. Add another cake layer and another cup of frosting. Top with the final cake layer and use another cup of frosting to add a crumb coat on the top and sides of the cake. Freeze the cake for 20 minutes. (See the recipe notes.)
Take the cake out of the freezer and add a second layer of frosting to the sides of the cake (not the top). Spread it on using an offset spatula and use the spatula or a scraper to smooth the edges. Wipe the blade clean frequently to achieve a smoother finish. Place the cake in the refrigerator.
Prepare the first batch of chocolate ganache for the drip. Pour 1/4 cup + 1 tbsp of milk chocolate chips and 2 tbsp + 2 tsp of heavy cream in a glass, heatproof bowl. Place the bowl over a small sauce pan that's about 1/2 full of water (make sure the water doesn't touch the bowl). Melt over medium heat, stirring frequently with a wooden spoon. Once the chocolate is almost melted remove the bowl from the heat and whisk until it's completely melted and smooth. Let the ganache stand for 10 minutes.
Take the cake out of the refrigerator and pour the ganache into a squirt bottle or piping bag. Hold it at a 45-degree angle along the top edge of the cake and gently squeeze. Apply varying levels of pressure on the bottle/bag as you pipe around the entire top of the cake. Varying levels of pressure achieves varying drip lengths. Let the drip stand for 5 minutes and then carefully add sprinkles. (I added sprinkles to every other drip.) Place the cake in the freezer.
Take the cake out of the freezer after 10 minutes. Place another cake board on top of the cake and carefully flip it over. The original top is now the bottom of the cake! Remove the original cake board and frost the top of the cake. Place it back in the refrigerator.
Prepare the second batch of ganache. Pour 1/2 cup + 2 tbsp of milk chocolate chips and 1/3 cup of heavy cream in a glass, heatproof bowl. Place the bowl over a small sauce pan that's about 1/2 full of water (make sure the water doesn't touch the bowl). Melt over medium heat, stirring frequently with a wooden spoon. Once the chocolate is almost melted remove the bowl from the heat and whisk until it's completely melted and smooth. Let the ganache stand for 10 minutes.
Repeat the drip step explained above. Before adding the sprinkles, pour the remaining ganache on top of the cake and smooth it out using an offset spatula. Then let it rest for 3-5 minutes before adding the sprinkles. Pipe the remaining frosting around the top of the cake to create a border. I used the Wilton #1M tip. Top with more sprinkles.
Store the cake in the refrigerator, but bring it to room temperature before serving. Enjoy!