Preheat oven to 350 degrees F. Line two cupcake pans with paper liners.
In a medium bowl, add in the melted butter, vegetable oil, and cocoa powder. Whisk until smooth.
Add in the buttermilk, sour cream, and vanilla. Continue to whisk until the sour cream is incorporated.
Whisk in the eggs until combined.
In a large mixing bowl, add in cake flour, sugar, baking soda, baking powder, and salt. Stir until blended.
Pour the cocoa mixture into the bowl with the dry ingredients. Whisk until everything is combined and most of the lumps have disappeared.
Fill each cupcake liner ¾ full.
Place in the preheated oven and bake for 18 - 23 minutes until done. Insert a toothpick or skewer in the center of the cupcakes in the middle of the cupcake pan, if they come out clean or with moist crumbs, they're done.
Let the cupcakes cool for about 15 minutes and then turn onto a cooling rack to finish cooling.
Chocolate Buttercream Frosting
In a large mixing bowl, add the butter. Mix with a hand mixer on medium until creamy.
Add in the powdered sugar, sifted cocoa powder, heavy cream, and vanilla extract.
Beat on high until frosting a thick and creamy.
Place the chocolate frosting in a piping bag fitted with the Wilton 1M piping tip and pipe tall swirls on each coooled cupcake.
Sprinkle chocolate sprinkles on top of the frosted cupcakes. The frosting will crust, so quickly add the sprinkles so they will stick to the freshly piped frosting.
Place the frosted cupcakes in an airtight container and store them at room temperature.