01 - Cream the softened butter and brown sugar in a small bowl until light and fluffy. Whisk in the milk and vanilla extract until smooth. Stir in the heat-treated flour and salt until fully combined, then fold in the mini chocolate chips. Portion into 12 small balls (approximately 2 teaspoons each), arrange on a parchment-lined plate, and refrigerate until firm.
02 - Combine the unsalted butter and chopped dark chocolate in a heatproof bowl. Melt using the microwave in 30-second intervals, stirring between each burst, or set over a double boiler. Stir until completely smooth and allow to cool slightly before proceeding.
03 - In a large mixing bowl, beat the granulated sugar, brown sugar, and eggs together for approximately 2 minutes until the mixture becomes pale and creamy. Drizzle in the vanilla extract and the melted chocolate mixture, mixing until thoroughly incorporated.
04 - In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and salt until evenly distributed. Add the dry mixture to the wet ingredients and fold until a thick, fudgy dough forms. Refrigerate for 10-15 minutes to firm for easier handling.
05 - Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
06 - Scoop approximately 2 tablespoons of brownie cookie dough for each cookie. Flatten the dough in the palm of your hand. Place one chilled cookie dough ball in the center and carefully wrap the brownie dough around it, pinching the edges to seal completely. Repeat for all remaining portions.
07 - Arrange the assembled cookies on the prepared baking trays, leaving adequate space between each for spreading. Bake for 10-12 minutes until the tops appear set with characteristic crackling across the surface. Avoid overbaking to maintain optimal fudgy texture.
08 - Allow the cookies to rest on the baking sheet for 10 minutes to set before transferring to a wire rack to cool completely.