Red White and Blue Glazed Shortbread Cookies

For the cookies:

1. Line 2 sheet pans with parchment paper. Set aside.
2. Place soft butter in a medium-size mixing bowl. Stir with a wooden spoon or sturdy spatula until nice and smooth. Add powdered sugar and vanilla. Mix together by hand for about 30 seconds, until fluffy and well blended.
3. Sprinkle the flour and cornstarch evenly over the top. Stir until flour is incorporated and the dough is shaggy.
4. Turn out onto a lightly floured surface and press dough in a ball. Knead a few times until smooth, then form into a ball again and press with your hands into a flat disk.
5. On a lightly floured work surface, roll out dough to a ⅜-inch thickness. Keep work surface, dough and rolling pin lightly dusted with flour. Cut out cookies and place on prepared pans. Re-roll scraps as many times as needed to use up the dough.
6. Place cutouts in the refrigerator for at least one hour or up to 24 hours.
7. When ready to bake, preheat oven to 350˚F. Remove cookies from the refrigerator and bake for 12-16 minutes or until just beginning to turn golden at the edges. Rotate pans halfway through for even browning. Cool completely before glazing.

For the glaze:

1. Combine powdered sugar, half and half and ¼ teaspoon lemon (or your favorite flavor) extract in a medium-size bowl. Mix until smooth. The glaze should be thick but pourable. Add a little more half and half if too thick. Taste the glaze and add more extract, if needed (see the ​note above in the post).
2. Transfer half of the glaze to a small bowl. With a toothpick, add a small amount of red and blue gel food coloring and swirl it just a bit. Don’t swirl too much or the icing will become murky. Use a light hand with the gel food coloring. A little goes a long way!
3. Dip one cookie at a time into the glaze. Let the cookie sit on the top of the glaze and gently push down at all the edges to ensure the surface of the cookie is covered with the glaze. With your thumb and forefinger, pull the cookie out of the glaze and allow the excess icing to drip off into a separate bowl. Then quickly flip the cookie right side up and give it a gentle jiggle to allow the glaze to flow evenly over the surface. Repeat with remaining cookies. (See video above for a demonstration of this technique>)
4. Add more of the white glaze to the bowl when needed. Repeat adding more gel coloring as needed.
5. Sprinkle with red, white and blue sprinkles (or other colors) while wet, if desired.
6. Allow the cookies to dry on a wire rack for at least 2 hours after glazing, then store in an airtight container.