Microwave the frozen blueberries for about 30 seconds until fully thawed and jammy. Set them aside without draining any of the natural juices.
Beat the cold, cubed unsalted butter and granulated sugar together in the bowl of a stand mixer on high speed for about 2 minutes, until smooth and well combined.
Mix the thawed blueberries and all of their liquid juices into the butter mixture. Beat until incorporated, allowing the blueberries to naturally puree and dye the dough.
Stir the all-purpose flour, baking powder, and sea salt into the wet ingredients until a soft, slightly sticky dough forms.
Fold in the white chocolate chips gently to distribute them evenly. Place the mixing bowl in the refrigerator to chill the dough for 20 minutes.
Preheat your oven to 350 degrees Fahrenheit and line a large baking sheet with parchment paper while the dough finishes chilling.
Scoop the chilled cookie dough onto the prepared baking sheet using a cookie scoop. Gently press down on each dough ball to flatten it slightly, as these cookies do not spread much in the oven.
Bake for 10 to 12 minutes, or until the cookie edges are firm and the centers are just set. Do not overbake to ensure they stay soft.
Remove the baked cookies from the oven and let them rest on the baking sheet for 10 minutes before carefully transferring them to a wire rack to cool completely.