Preheat the oven to 350°F (175°C) and line a cupcake pan with liners.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt.
In another bowl, combine the melted butter, eggs, vanilla extract, and milk.
Pour the wet ingredients into the dry ingredients and stir until just combined; fold in the chocolate chips.
Divide the batter evenly among the lined cupcake cups, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick comes out clean.
Allow the cupcakes to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
While the cupcakes cool, prepare the frosting. In a mixing bowl, cream the butter until light and fluffy.
Gradually add the confectioners' sugar and cocoa powder, mixing until fully combined.
Pour in the milk, mixing until the frosting reaches the desired consistency.
Frost the cooled cupcakes generously with the chocolate frosting.
