• Preheat oven to 350°F (175°C). Line 2 cupcake pans (24 cupcakes) with cupcake liners.
• In a large bowl, whisk together the flour, granulated sugar, brown sugar, cocoa powder, espresso powder, baking soda, baking powder, and salt.
  1 1/3 cups all-purpose flour, 3/4 cup granulated sugar, 2/3 cup brown sugar, 2/3 cup cocoa powder, 2 tsp espresso powder, 1 1/2 tsp baking soda, 1 tsp baking powder, 1/2 tsp salt
• In another bowl, combine the buttermilk, coffee, vegetable oil, eggs, and vanilla extract.
  3/4 cup buttermilk, 1/2 cup coffee, 1/2 cup vegetable oil, 2 eggs, 2 tsp vanilla extract
• Add the wet ingredients to the dry ingredients, stirring just until combined. Be careful not to overmix.
• Pour the batter into the cupcake liners, filling each about half full. Bake for about 18-20 minutes, or until a toothpick inserted in the center comes out clean.
• Remove the cupcakes from the oven and let them cool in the tin for a few minutes, then transfer to a wire rack to cool completely before frosting.

Frosting

• Beat the butter with the whisk attachment in a stand mixer until it's creamy and fluffy (about 5-7 minutes).
  1 cup butter
• Gradually add the chilled sweetened condensed milk, ¼ can at a time, while continuing to beat. The mixture should become light and fluffy.
  14 oz sweetened condensed milk
• Stir in the melted chocolate, vanilla extract, and espresso powder until evenly incorporated.
  1/3 cup chocolate chips, 1 tsp vanilla extract, 3 tsp espresso powder
• Once the cupcakes are completely cool, use a piping bag or an offset spatula to frost them with the mocha frosting.
• Decorate (Optional): You can garnish with chocolate shavings, a dusting of cocoa powder, or espresso beans for an extra touch.