Preheat oven to 350 degrees. Line a 9x9x2-inch baking pan with foil; set aside.
In a medium mixing bowl stir together 1 cup flour and the brown sugar. Cut in the 1/2 cup butter until mixture resembles coarse crumbs.
Stir in the 1/4 cup mini chocolate chips. Press into prepared pan. Bake for 8 minutes. While shortbread crust is baking, you can mix up the brownie batter.
In a large mixing bowl, stir together granulated sugar, 3/4 cup flour, unsweetened cocoa powder, baking powder, and salt.
Add eggs, melted butter, and vanilla; beat by hand until smooth. Stir in the 1/2 cup mini chocolate chips. Carefully spread over crust in pan.
Bake 40 minutes more. Cool brownies in pan on a wire rack.
Lift brownies out of pan by lifting up on foil. Cut into bars. Makes 24 bars (unless you cut them bigger like I did; then you’ll get about 16).
If you want to make a bigger batch, you could double the recipe and make them in a 9×13 inch pan…the baking time may be a little longer.
Recipe by Baker Street at https://bakerstreet.tv/2013/02/shortbread-brownies/