01 -
Combine unsalted butter, granulated sugar, powdered sugar, and orange zest in a stand mixer fitted with a paddle attachment. Mix on medium-low speed for about 1 minute until smooth and creamy. Avoid high speed to prevent aeration.
02 -
Add the whole egg and vanilla extract to the creamed mixture. Continue mixing on medium-low speed until fully combined.
03 -
Introduce kosher salt, cornstarch, all-purpose flour, cake flour, and finely chopped chocolate. Mix on medium-low speed just until a cohesive dough forms.
04 -
Turn the dough onto a sheet of plastic wrap and form into a 23–25 cm log. Wrap tightly and refrigerate for at least 2 hours to firm.
05 -
Preheat oven to 175°C. Line a half sheet pan with parchment paper. Unwrap the chilled dough and slice into 0.6 cm thick rounds.
06 -
Arrange slices on the prepared baking sheet, spacing at least 2.5 cm apart. Bake for 10–13 minutes or until the edges are lightly golden.
07 -
Transfer baked cookies to a wire rack to cool for at least 15 minutes before serving. For optimal chocolate texture, allow to cool for 45 minutes for the chocolate to set. Store in an airtight container at room temperature for up to one week.