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. 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.
Pit cherries to make cherry puree. Place the cherries in a blender and puree until smooth. Measure 1/2 cup of puree and set aside.
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 and cherry puree, 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 and isn't too wet.
Place chocolate chips in a medium heat-proof bowl.
In a small pot over low heat, heat the heavy cream until just before boiling.
Pour the heavy cream over the chocolate chips. Allow the mixture to stand for 1-2 minutes.
Use a spatula to stir the mixture until smooth.
Allow the ganache to come to room temperature before adding it to the cake.
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.
Evenly place chopped cherries on top of the buttercream.
Spread more buttercream on top of the cherries. This will help seal the cherries into the buttercream and prevent the juice from seeping into the cake.
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 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. Place the cake in the fridge for 20-30 more minutes.
Once the ganache is room temperature, use a spoon to drizzle the ganache around the sides of the cake, allowing it to drip down the sides. Fill in the middle of the cake with ganache and spread evenly with the back of the spoon. Allow the ganache to set for 10 minutes.
Place mini chocolate chips around the outside of the cake.