Black Velvet Cupcakes

Preheat the oven to 350 degrees f. Combine black cocoa powder and hot milk in a small bowl and whisk together and set aside.
Combine sugar, vegetable oil, melted butter, eggs and egg yolk, vanilla extract, vinegar, and milk in a large mixing bowl. Whisk together until combined.
In a separate large bowl, combine all purpose flour, baking powder, kosher salt, and baking soda. Add half of the dry ingredients to the wet ingredients and then pour in the black cocoa mixture. Add the remainder of the flour mixture and mix with a rubber spatula until just combined.
Line a muffin tin with cupcake liners and fill each liner about 2/3 with the cupcake batter. Back for 18-20 minutes. Allow the cupcakes to cool completely on a wire rack.
Make the black cocoa frosting - melt chocolate chips and corn syrup in the microwave in 15 second increments until melted. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter for 2 minutes, then add cream cheese and beat together for 1 minute. Then add powdered sugar and black cocoa. Continue to mix together until combined, then add melted chocolate mixture and heavy cream.
Scrape down the sides of the bowl of your stand mixer and continue to mix for another minute. You can add a couple drops of black food coloring for a true black frosting.
Add the black cocoa buttercream to a piping bag and pipe the icing onto the cooled cupcakes.