Preheat your oven to 350°F and line a cupcake pan with liners.

In a small bowl, sift together the flour, cocoa powder, espresso powder (if using), baking powder, baking soda, and salt. Set aside.

In a large bowl, cream together the granulated sugar and softened butter until fluffy.

Add the egg, egg yolk, and vanilla to the sugar mixture, mixing until pale and smooth.

Mix in the sour cream and milk until combined.

Gradually add the dry ingredients to the wet ingredients, mixing until smooth.

Divide the batter among the cupcake liners and bake for 17-19 minutes, or until a toothpick inserted into the center comes out clean.

Let the cupcakes cool completely on a wire rack.

Heat the heavy cream until just boiling, then pour it over the chocolate chips in a bowl.

Let it sit for a minute, then stir until smooth. Allow the ganache to cool to room temperature.

In a microwave-safe bowl, combine the hot cocoa mix and heavy cream. Microwave for 15-20 seconds, then stir until smooth. Let it cool to room temperature.

In a large bowl, beat the softened butter and salt until pale and fluffy.

Gradually add the cooled hot cocoa mixture and powdered sugar to the butter, mixing until light and fluffy.

Stir in the vanilla extract and cocoa powder until well combined.

Remove a bit of the centers of the cooled cupcakes and fill each with chocolate ganache.

Pipe a generous amount of hot cocoa frosting onto the tops of the cupcakes.

Store any leftovers in an airtight container for up to three days.

Get ready to savor the ultimate chocolatey goodness with these Hot Cocoa Cupcakes!