Stir melted butter, brown sugar, and granulated sugar in a medium bowl. Add milk and salt and stir, then stir in flour. Stir in chocolate chips. Scoop 12 1-tablespoon balls of dough onto a cookie sheet covered with wax paper. Divide the remaining dough into 12 balls for topping the cupcakes. Chill until cupcake batter is ready.

Preheat oven to 350°. Line cupcake tins with liners.

Whisk flour, sugar, cocoa, baking soda, and salt in a large bowl.

Whisk hot water, oil, vinegar, and vanilla in a large measuring cup.

Add liquid ingredients to wet ingredients and whisk until smooth.

Divide batter among liners, filling approximately half full. Add one cookie dough ball to each cupcake, pressing lightly to mostly have it covered with batter.

Bake for 15-20 minutes until a toothpick comes out clean. Cool before frosting.

Beat the butter until smooth in a large bowl or stand mixer. Add brown sugar and beat until creamy and fluffy, 2-3 minutes.

Add vanilla, heavy whipping cream and salt and mix until combined.

Reduce mixer to medium-low speed and while mixer is running, slowly add powdered sugar and mix until smooth, about 1-2 minutes. Then increase the mixer to medium-high and beat until fluffy and light, about 5 minutes.

Frost cupcakes as desired, sprinkling with extra mini chocolate chips and/or a mini cookie.