Preheat the oven to 350°F. Line 2 regular-size cupcake pans with parchment cupcake liners.

Add the flour, cocoa powder, baking powder, and baking soda to a large mixing bowl. Whisk to combine.

Whisk in the granulated sugar and salt to the flour mixture.

Whisk in the sour cream, vegetable oil, and vanilla extract until well incorporated.

Whisk in the eggs, one at a time, whisking until there are no streaks of yellow or egg whites remaining.

Carefully whisk in the boiling water. Whisk until the batter is smooth.

Fill the cupcake liners ⅔ full with batter. Bake for 22 to 25 minutes or until a toothpick inserted comes away clean. Allow the cupcake to cool completely.

Using either a stand mixer, or a large mixing bowl and a handheld mixer, on medium-high speed, beat the butter, cocoa powder, and vanilla for 1½ to 2 minutes or until smooth.

Add the powdered sugar 1½ cups at a time, beating well after each addition. Alternate between adding powdered sugar and 2 to 2½ tablespoons of heavy cream at a time. Continue beating until the frosting is smooth.

Add the frosting to a disposable piping bag fitted with a large decorator’s tip (such as 1M, 2D, or 4B. I used 4B). You can also use a gallon-size ziplock bag with a corner snipped off. Hold the tip about a ½ inch above the surface of the cupcake. Starting on the outside of the cupcake, use even, steady pressure to squeeze the frosting in a spiral working in towards the center of the cupcake. (You can also start in the center and work your way out to the edge if you prefer) Shake the chocolate sprinkles over the frosting. Repeat for the remaining cupcakes.