Preheat your oven 350 F and line your baking tray with parchment paper and set aside. In a large bowl, mix the dry ingredients - flour, cornstarch, and salt together and set aside.
In a stand mixer (you can also go ahead and use the hand mixer for this) add in the butter and sugar and beat it at medium speed, scraping down the sides for at least 2-3 mins.
Add in the eggs and vanilla extract and beat until everything is incorporated well.
Add the flour mixture to the butter-egg mixture in batches and mix it well to form the dough. Flatten the dough and wrap it with a cling wrap and refrigerate for at least an hour.
Once chilled, roll out the dough to 1/4 inch thickness and cut out tree-shaped cookies. Also, cut out the center of half of the cookies using the same shape cutter in a smaller size. Place them on the prepared baking tray and bake for about 12 minutes or until edges are slightly golden.
Apply a thick layer of strawberry jam to the bottom of the whole cookie, but leave a thin border around each cookie and place the corresponding cut-out cookies on top of it carefully.
Next, using a spoon fill the cut-out centers of the cookies with some more jam.
Notes
These can be doubled for gift giving or holiday gatherings.