In the bowl of a stand mixer fitted with the paddle attachment, beat together the sugar, flour, cocoa powder, baking powder and salt.
Beat in the eggs, melted butter, and vanilla extract until the mixture is smooth then stir in the miniature chocolate chips. Carefully spread the brownie mixture over the shortbread in the pan.
Return the pan to the oven and bake the brownies for an additional 40 minutes.
Remove the brownies from the oven then let them cool completely in the pan. Using the foil, lift the brownies out of the pan and cut them into 24 pieces and serve.
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