Dark Chocolate Cocoa Nib Shortbread

Name: Dark Chocolate Cocoa Nib Shortbread
Ingredients: 3/4 cup (4 oz./125 g) all-purpose flour, plus more for dusting; 1/2 cup (2 1/2 oz./75 g) white whole wheat flour (ivory wheat flour); 1/2 cup (1 1/2 oz./45 g) unsweetened cocoa powder; 1 Tbs. cornstarch; 1/2 tsp. sea salt; 1/2 tsp. baking soda; 12 Tbs. (1 1/2 sticks) (6 oz./185 g) unsalted butter, at room temperature; 1/4 cup (2 oz./60 g) granulated sugar; 3/4 cup (6 oz./185 g) firmly packed light brown sugar; 1 1/2 tsp. vanilla extract; 1/3 cup (1 1/2 oz./45 g) cocoa nibs; Confectioners’ sugar for dusting