In a sauce pan, heat frozen blueberry over medium high heat until soft and jammy. Set aside.

In a large bowl, whisk together gluten free flour, cornstarch, baking powder, and salt. Set aside.

In a small bowl, stir the rest of the cornstarch with water until well combined. Set aside.

In a mixing bowl, cream butter and sugar with electric mixer on high speed. Mix until creamy, and almost all the sugar dissolved about 3 minutes. Don’t forget to scrape the sides of the bowl.

Add cornstarch mixture, milk, and cooled blueberry jam and mix again over low speed. Add the flour mixture and mix until just combine. The cookie mixture will be sticky. Scrape the sides of the bowl with a spatula as necessary.

Cover the dough with plastic wrap and refrigerate for 2½ hours before baking.

After 2½ hours, preheat oven to 350°F or 175°C.

Scoop cookie dough with 2 tablespoon scoop then roll the dough into a balls and place it on a baking sheet lined with parchment paper. Place cookie dough 2 inch apart.

Bake for 13 minutes. While the cookies are baking, store the remaining cookie dough in a fridge.

Let them cool on the baking sheet for 5 minutes. Transfer the baked cookies to a cooling rack to let the cookies completely cool. Enjoy!