In a medium bowl, combine the flour, cornstarch, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment or a large bowl, beat together the butter and granulated sugar until light and fluffy.
Beat in the egg yolk, followed by the vanilla and almond extracts.
Add the flour mixture and beat in just until no streaks of flour remain.
Cover the bowl with plastic wrap and refrigerate for 30 minutes to 1 hour, until firm enough to handle without sticking.
Line two baking sheets with parchment or lightly grease.
Break off a 1 inch (2.5 centimeter) piece of dough and roll into a ball. Place on the prepared baking sheet.
Use your thumb or the back of a 1/2 teaspoon to slightly flatten the ball in the center, making an indention. If any cracks form around the edges, gently press them back together. Repeat with the remaining dough, placing them on the prepared baking sheet 1 inch (2.5 centimeters) apart.
Place the baking sheets in the refrigerator for 15 minutes and preheat the oven to 350˚F (180˚C).
Place the chilled baking sheets in preheated oven and bake the cookies just until set and barely golden on the bottom, 10-12 minutes.
Allow the cookies to cool for 5 minutes, then remove to a wire rack to cool completely to room temperature. If the indentations are too shallow, lightly press down to make them more pronounced while still warm.