In the bowl of a stand mixer, beat the butter on low speed to smooth and soften. (Do not over-beat it; the goal is not to incorporate air, but rather to make sure there will be no lumps of butter in the final product.)

Add the sugar and the salt to the butter and cream it on medium-low speed until it has combined and slightly lightened. Scrape the sides and bottom of the mixer bowl to make sure there are no under mixed bits.

Add the whole egg, egg yolk, vanilla, and almond extract and mix on medium-low speed until fully combined and emulsified. 

Add the flour and cornstarch all at once and mix on low speed until the mixture starts to form a dough and the flour disappears. Scrape the sides and bottom of the bowl to make sure there are no dry bits of flour. 

Drop the dough onto lightly floured parchment paper. Gently form the dough with your hand into a smooth square/rectangle before lightly flouring the top of the dough. Place a second piece of parchment paper over the top of the dough and roll it to 1/4″ with a guided rolling pin. (Feel free to roll the dough to your preferred thickness.) 

Refrigerate the sheet of dough for one to two hours or overnight.

When ready to bake, preheat the oven to 400 F.

Cut shapes from the chilled dough with lightly floured cookie cutters, placing the cut cookies on a parchment lined baking sheet. Chill the cookies in the refrigerator for 10-15 minutes or in the freezer for 5 minutes before baking. Bake the cookies for 8-10 minutes, or until the tops are no longer shiny. The size and thickness of the cookies will determine how long they bake, so pay attention to the surface and the bottoms of the cookies. The surface should be no longer shiny, and the bottoms should be nearing golden brown.

Cool the cookies on the cookie sheet for a few minutes before transferring them to a wire rack to cool completely before decorating. Moving them prematurely can result in broken cookies.

Decorate how you would like with buttercream or royal icing.