Preheat oven to 350F. Line 9"x13" baking pan with foil (with ends long enough to fold over the edge) and spray with nonstick spray. Set aside.
Combine all shortbread ingredients in the bowl of a food processor. Pulse until mixture resembles coarse crumbs and begins to clump together.
Press mixture into the bottom of the prepared pan. Prick the dough all over with a fork. Freeze 5 minutes. Bake until lightly browned, about 30 minutes.
For Brownies:
While the shortbread is baking, prepare the brownies. In a small bowl, combine dry ingredients (flour, cocoa, salt, and baking powder). Set aside.
In a large heatproof bowl, combine butter and chocolate. Warm in microwave until smooth on 30-second intervals, stirring after each interval.
Once chocolate mixture is smooth, stir in sugar, vanilla extract, and chocolate extract and mix to combine. Then add the eggs, one at a time, mixing to incorporate after each addition. Add dry ingredients and stir until just combined.
Pour brownie batter over browned shortbread crust. Bake 30 minutes, or until the top of the brownies appear dry. Let cool completely on a wire rack before cutting.Enjoy!
Notes
Note on chocolate extract: I highly recommend this (sometimes overlooked) extract! It lends an amazing depth of flavor to chocolate baked goods! If you can't find it in your local grocery store, you can find some [here]. Even better, makes yourself some [Homemade Chocolate Extract] for next time!Note on espresso beans: I used the ground espresso beans pictured in my post. They were available at my local grocery store. If you can't find ground espresso beans at your local store, you can find them [here]. Alternatively, you could substitute espresso powder.