Preheat your oven to 350F.
Bring 1 cup of water to a boil.
In one bowl, add your cake flour, unsweetened cocoa powder, baking powder, baking soda, and salt. Stir to combine.
In another, add your butter, sugar, vanilla extract, sour cream, eggs, and melted chocolate. Stir to combine.
Slowly add your dry ingredients into the wet ingredients. The mixture will become thick at this point.
To the mixture, you are going to add the one cup of boiling water. This will change the consistency into a very thin almost liquid like mixture.
Add your mixture to two cake pans and cook in an oven at 350F for 25 minutes. (To know if it is done, stick a knife in the middle of the cake, and when it comes out clean, the cake is ready!)
While the cake is in the oven, prepare your buttercream frosting. To do so, combine your softened butter, cocoa powder, powdered sugar, and vanilla extract into a bowl. Mix to combine. Slowly add your milk while whipping the frosting until you reach a smooth and fluffy consistency. Set aside.
After your cake is out of the oven, allow the cake to cool to room temperature. Remove the cake from the pans. spread your caramel over the bottom layer of the cake and stack the top layer on top. After, spread your buttercream frosting on top. Serve and enjoy!