Preheat oven to 350 degrees F. Line two cupcake pans with paper liners.
In a medium bowl, add in the melted 1/4 cup butter, 1/2 cup vegetable oil, and 3/4 cup unsweetened cocoa powder. Whisk until smooth.
Add in the 1 cup buttermilk, 1 cup full-fat sour cream, and 2 teaspoons vanilla extract. Continue to whisk until the sour cream is incorporated.
Whisk in the 2 large eggs until combined.
In a large mixing bowl, add in 1 1/2 cups cake flour, 1 1/2 cups granulated sugar, 1 1/2 teaspoons baking soda, 1/2 teaspoon baking powder1 teaspoon 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 3/4 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 1 cup butter. Mix with a hand mixer on medium until creamy.
Add in the 4 cups powdered sugar, sifted ½ cup unsweetened cocoa powder, ¼ cup heavy whipping cream, and 2 teaspoons 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 1 tablespoon 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.
Notes
Storage: Store in an airtight container at room temperature for up to 5 days.