• Preheat the oven to 350°F. Make a foil sling for an 8-inch square baking pan by folding 2 long sheets of aluminum foil so each is 8-inches wide.  Lay the sheets of foil perpendicular to each other, with extra foil hanging over the edges of the pan, smoothing foil flush to pan; set aside.

For the Shortbread

• In a medium bowl, stir together the flour, brown sugar and salt. Using a pastry blender, cut in the butter until mixture resembles pea-size crumbs. (Alternatively, you can pulse all the ingredients in a food processor.) Stir in the mini chocolate chips. Press the mixture evenly into the prepared pan. Bake for 8 minutes.

For the Brownie Batter

• Meanwhile, in a large bowl stir together the sugar, flour, cocoa powder, baking powder, espresso powder and salt. Add the eggs, melted butter and vanilla and stir the mixture until smooth. Add the mini chocolate chips and stir until combined.
• Remove the shortbread crust from the oven. Using an off-set spatula, carefully spread the brownie batter over the crust. Return the pan to the oven and bake for another 45 minutes or until a toothpick inserted in the center of the batter comes out clean. Cool completely on a wire rack. Using the edges of the foil, lift the the brownies out of the pan and cut into bars. Enjoy!