Preheat the oven and line a square baking pan with parchment paper for easy removal. Melt the butter and chocolate chips together until smooth then whisk in both types of cocoa powder. In a separate bowl whisk the sugars, eggs, egg yolk, and vanilla extract vigorously to help create a shiny top. Combine the melted chocolate mixture into the egg mixture until smooth. Gently fold in the flour, espresso powder, and salt with a spatula just until combined. Spread half of the batter into the pan and layer the whole cookies in a grid. Cover the cookies with the remaining batter and top with chopped cookie pieces. Bake until a toothpick comes out with moist crumbs and let cool completely before slicing.