Preheat your oven to 350ºF (175ºC) and line a cupcake tray with 12 cupcake liners.

Boil about 1 cup of water and set it aside to cool slightly.

In a large mixing bowl, sift together the dry ingredients: flour, sugar, cocoa powder, espresso powder, baking powder, baking soda, and salt.

In another bowl, whisk together sour cream, vegetable oil, eggs, vanilla extract, and the cooled boiling water.

Gently fold the wet ingredients into the dry mixture until just combined.

Divide the batter evenly among the cupcake liners, filling each about two-thirds full. Bake for 17–20 minutes.

For the hot fudge, combine sugar, agave syrup, and milk in a saucepan over medium heat and stir until bubbling.

Remove from heat and pour it over chopped chocolate and cocoa powder in a bowl. Mix in butter and vanilla until smooth.

Beat room temperature butter until fluffy, and gradually add sifted powdered sugar; incorporate milk until smooth.

Once cooled, use a knife to remove the center of each cupcake and fill with hot fudge. Reserve some fudge for drizzling.

Frost the tops of your cupcakes with buttercream and drizzle reserved hot fudge over the frosting.

Garnish with mini marshmallows and crushed candy cane.

Serve and enjoy!