In a large bowl of an electric mixer fitted with the paddle attachment or using a hand held mixer, beat the softened butter or vegan baking stick and the granulated sugar until soft and creamy. About 2-3 minutes.
In a small bowl, using a spoon, mix together the cornstarch and water until thin and watery. It will be thick and tacky at first.
With the mixer on low speed, beat in the cornstarch water mixture. Then beat in the vanilla and milk. The mixture might look slightly chunky and that’s ok.
In a separate large bowl, whisk together the gluten free flour, the baking powder and the kosher salt.
Still on low speed, beat the gluten free flour mixture into the wet ingredients, a little at a time until just combined.
Once combined, scrape down the sides of the bowl using a spatula.
Shape the dough into a disc, cover with plastic wrap and refrigerate for at least 30 minutes.
After 30 minutes, preheat the oven to 325 degrees Fahrenheit. Line a baking sheet with parchment paper. Set aside.
Take the dough out of the fridge. Using a small cookie scoop, scoop the dough out. If you don't have a cookie scoop, roll the dough into 1 inch balls.
Drop each dough ball into a small bowl of the red sugar and coat completely.
I only put about 12 cookies on the tray at a time. Make sure to space them at least 3 inches apart. Put the extra dough back into the fridge in between batches.
Bake the cookies in the middle rack for 11 minutes.
While the cookies are baking, line a small baking sheet with parchment paper.
When the cookies come out of the oven, reshape if needed (see FAQS in blog post) and immediately gently press a chocolate heart into the center of each cookie.
Immediately transfer cookies to the other lined baking sheet and freeze for 15 minutes to prevent the heart from melting.
Once the cookies are frozen for 15 minutes, store in an airtight container at room temperature. Enjoy!