1 ¾ cups all-purpose flour
¼ cup cornstarch
¼ teaspoon kosher salt
6 ounces (1 ½ sticks) unsalted butter, at room temperature
1 cup powdered sugar
1 tablespoon grated Bergamot orange zest
2 tablespoons freshly squeezed Bergamot orange juice
Preheat the oven to 350˚F. Whisk together the flour, cornstarch, and salt in a medium bowl. In a mixer fitted with a paddle attachment, beat together the butter and 1/3 cup of the powdered sugar on medium until creamy. Add the orange zest and juice and mix on low until blended. Add the dry ingredients and mix on low until the dough comes together, stopping the mixer once or twice to scrape down the sides of the bowl. Scoop the dough by the tablespoonful onto parchment-lined baking trays, roll each scoop of dough into a ball, and arrange the balls about an inch apart. Bake for 16 to 18 minutes, or until lightly browned on the bottom but still pale on top. Transfer cookies to a rack and let cool for about half an hour, or until barely warm. Roll each cookie in the remaining 2/3 cup of powdered sugar to coat.
Makes 32 to 34 cookies. Use lemons or limes if Bergamot oranges are unavailable. Cookies keep for several days in a tightly sealed container in a cool, dry place. Perfect with a cup of Earl Grey tea.