Preparation Steps

• Preheat oven to 350°F (175°C). Line an 8-inch square baking pan with aluminum foil and spray with cooking spray.
• For the shortbread crust: In a stand mixer fitted with a paddle attachment (or in a large bowl with an electric mixer), combine the softened butter, flour, confectioners' sugar, cornstarch, vanilla extract, and salt. Beat on low speed until a dough forms, about 3-4 minutes.
  0.5 cup unsalted butter
• Press the dough evenly into the prepared pan to form a smooth, flat layer. Use a spatula or your fingers to smooth it.
• Pierce the crust all over with a fork to allow steam to escape.
• Bake for 12-13 minutes, or until the crust is just set. It should remain pale in color.
• While the crust bakes, prepare the filling. In a small bowl, whisk together the corn syrup, water, and vanilla extract. Set aside.
  0.5 cup unsalted butter
• In the same mixer bowl (wiped clean), beat the softened butter, granulated sugar, and salt on medium-high speed until smooth and combined, about 2-3 minutes.
  0.5 cup unsalted butter
• Add the eggs one at a time, beating well after each addition until smooth and combined. Scrape down the sides of the bowl as needed.
  0.5 cup unsalted butter
• With the mixer on low speed, add half of the flour and half of the corn syrup mixture. Beat until just combined. Add the remaining flour and corn syrup mixture and beat until smooth.
  0.5 cup unsalted butter
• Stir in the mini chocolate chips until just combined.
  0.5 cup unsalted butter
• Pour the filling evenly over the baked crust. Use a spatula to smooth it into an even layer.
• Sprinkle the remaining 2 tablespoons of mini chocolate chips evenly over the top.
  0.5 cup unsalted butter
• Bake for 23-25 minutes, or until the edges are set and the center is mostly set with a slight jiggle. The top should have a few lightly golden brown spots. Be careful not to overbake.
• Let the bars cool completely in the pan on a wire rack for at least 2 hours before slicing and serving.