Strawberry Jam Thumbprint Cookies

In a large mixing bowl fitted with the paddle attachment, cream together the butter and sugar on medium speed until light and creamy, about 3 minutes. Add egg yolk, vanilla and almond extract and mix until combined.
Add in salt, cornstarch and flour, being careful not to over mix.
Line a cookie sheet with parchment paper.
Scoop dough into 1½ tablespoon size balls and roll with your hands to make a tight ball. This will help them from cracking too much. Then roll the balls in sugar.
Place cookie balls on the cookie sheet. Using a teaspoon measuring spoon, press into the cookie balls and create an indention in each cookie. Using that same measuring spoon, fill each cookie indention with jam.
Preheat your oven to 350. While your oven is preheating place your cookies in a freezer, or fridge if needed, and allow the dough to chill while oven warms. Ideally 20 minutes.
Place chilled cookie dough on 2 cookie sheets so that there is space between cookies. Bake for 12-14 minutes, or until a light golden brown rim starts around the edge of the cookies. Allow to cool completely before moving and eating.