In a bowl, whisk together the flour, cornstarch and salt. Set aside.
In another large bowl, beat the butter and sugar on high speed until creamy using a hand mixer or a stand mixer, about 2-3 minutes.
Add the egg and vanilla and beat for another minute, scraping the sides of the bowl if necessary to fully combine.
Slowly add the flour mixture to the egg mixture and mix on low speed until thoroughly combined and the dough forms. If the dough is too wet, add a little more flour, a tablespoon a time, until it comes together. It’s perfect when you are able to pick up the dough in one piece.
Divide the dough in half.
Using a toothpick, add a tiny amount of food coloring (if using) to one half of the dough and knead by hand until the dough is fully colored.
Roll out each batch of dough between 2 sheets of parchment paper to your desired thickness (I roll out mine about ¼ inch / 0.5 cm thick).
Put the dough in the freezer for 15 minutes.
Cut each batch of dough into ½ inch (1 cm) strips.
For one batch of dough, slightly separate the strips by quickly pushing a knife left & right in between each cut to create tiny gaps. Put the dough in the freezer again for 10 minutes.
Meanwhile, preheat the oven to 350°F / 175°C.