Preheat oven to 325°F (163°C). Line a 12-count muffin pan with cupcake liners or spray with nonstick spray. Set aside.

Melt the chopped chocolate and sliced butter together in the microwave in 30-second increments, stirring after each until completely smooth and combined. Allow to cool for a few minutes. Stir in sugar, then vanilla. Add in eggs, 1 at a time, mixing well after each addition. Mix in the flour and salt.

Divide the batter evenly among the muffin cups and bake for 20–23 minutes. Mine took 22 minutes. A toothpick inserted in the center will have moist crumbs. Be careful not to overbake the cupcakes.

While the cupcakes are cooling in the pan, make the frosting. With an electric handheld mixer or stand mixer fitted with a paddle attachment, cream together the butter and sugar at medium speed. Add the vanilla and beat well. Stir in the flour and salt until doughy. Stir in the milk and beat until fluffy. Gently fold in chocolate chips. Frost cooled cupcakes.