Preheat the oven to 350º F.

Using butter, grease the bottom and sides of an 6 inch round cake pan or springform pan and line the bottom with a round piece of parchment paper. To ensure even baking, place a bake even strip around the pan. You can make your own homemade bake even strip by cutting a towel or shirt to fit the size of your pan. Get the fabric really wet, then squeeze out the dripping water but do not squeeze it too dry. Secure the fabric around the pan with a safety pin.

In a mixing bowl, combine the butter and sugar, beat using an electric mixer until fluffy. Add in the egg whites, beat again.

Add in the sour cream and vanilla extract, mix until smooth.

In a smaller bowl, combine the flour, baking powder and salt, gently mix with a spoon. Gradually add half of the flour mixture to the wet ingredients, do not dump it in, rather take spoonfuls of the flour mixture and gently shake it over the wet ingredients, as if you were sifting in the flour. Fold in the mixture until no flour remains. Repeat with the other half of the flour, folding it in and scraping the sides and bottom of the bowl to incorporate everything.

Add in the mini chocolate chips, and mix to combine.

Scrape the batter into the prepared cake pan, using a spatula to evenly spread it out.

Bake for 23-25 minutes, or until a toothpick inserted in the center comes out clean.

Once the cake is done, allow it to cool in the pan on a cooling rack for 10 minutes. After 10 minutes, carefully remove the cake from the pan. If using a springform pan, remove the sides and bottom. Allow the cake to cool completely on a cooling rack. Once cool, remove the parchment paper round from the bottom of the cake. If you need to level the top of your cake, do so now using either a cake lever or knife. Make sure the cake is completely cooled, then wrap the cake in plastic wrap and place it in the refrigerator. This cake is good for up to one week like this.

Repeat this recipe until all the cake layers are baked.

In a mixing large bowl, combine the butter and vegetable shortening, beat using an electric mixer until fluffy, 2 minutes.

Add in the vanilla extract, beat using electric mixer.

Begin to add the powdered sugar, about 1-2 cups at a time, mixing by hand first, then with the electric mixer. Continue adding powdered sugar until the frosting tastes good to you.

Add in your desired amount of gel food coloring. Start with a little and add more to get your desired color. Beat the frosting using the mixer one last time.

Spread a small amount of buttercream on a 6 inch round cardboard cake circle. Place your first layer of cake on top of the cardboard. Put buttercream on top of the first layer and spread it as even as possible with an offset spatula. Decide how much or how little frosting you want in-between each layer.

Repeat this process for each layer of cake. Once all of the layers are stacked and frosted, it’s time to do a crumb coat. The crumb coat will help seal the crumbs in. Using your offset spatula, spread a thin layer of buttercream around the sides and the top of the cake. It’s easiest to start off with more frosting on the cake and remove some as needed.

Place the entire cake in the freezer or fridge for 20 minutes to harden the crumb coat.

Begin to add the second layer of frosting, starting with the top of the cake and working your way down to the sides. Try to get the buttercream as even as possible around the cake.

To add sprinkles to the bottom of the cake, there are 2 options. 1. Put sprinkles in an open hand and gently push them into the frosting, filling in gaps as needed. 2. Lightly spray a piece of wax paper with non-stick cooking spray, place sprinkles on top of the sprayed area, then carefully place the wax paper against the cake (sprinkle side facing the cake) and gently rub your hand on the wax paper to get the sprinkles to stick to the cake. Fill in the gaps as needed.

To pipe a frosting border, place buttercream in a piping bag fit with a wilton 32 tip. Pipe the border using a continuous looping or corkscrew pattern.

To make the chocolate decorations for the top of the cake, melt 2 tbsp of colored candy melts with 1/2 tbsp vegetable shortening in a small microwave safe bowl for 30 seconds on 50% power. Stir and check the melts, and microwave longer as needed until they are melted. I would stick with 40-50% power so the candy melts don’t burn.

Allow the candy melts to cool slightly before transferring them to a squeeze bottle.

On a baking sheet covered with a piece of wax paper, begin to draw designs. You can use multiple colors and overlap them. Once you are done making them, place the designs in the fridge for about 2 minutes to harden up. Remove them from the fridge and begin to gently peel the wax paper off of the design. Place them on top of the cake.