Preheat oven to 350 degrees F (175 degrees C). Line a 12-cup muffin tin with paper liners.
In a large bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.
In a separate bowl, whisk together the melted butter and sugar until light and creamy. Whisk in the eggs, one at a time, then stir in the vanilla extract.
Add the dry ingredients to the wet ingredients and stir until just combined. Stir in the buttermilk until just incorporated.
Fill the muffin tin with the batter, about 2/3 full. Sprinkle each cupcake with the chocolate chips.
Bake for 20 minutes, or until a toothpick inserted into the center comes out clean.
Remove from oven and let cool completely before frosting.
To make the frosting, combine the fudge sauce and 1/4 cup butter in a small saucepan over medium heat. Stir until melted and combined.
Spread the fudge frosting on the cooled cupcakes and enjoy!
Interesting Facts
These cupcakes are best served at room temperature.
The cupcakes can be stored in an airtight container at room temperature for up to 3 days.
The cupcakes can also be frozen for up to 3 months.