Preheat your oven to 400°F. In a small bowl, whisk together the flour, baking powder, and salt.
Either in the microwave or on the stovetop, thaw the frozen blueberries until they are soft and jammy. If using the microwave, this should take about 30 seconds on high heat. If using the stovetop, it should take about 2-3 minutes on medium heat.
Let the blueberries cool for about 2-3 minutes. While they are cooling, use an electric mixer or a stand mixer to cream together the butter and sugar until the mixture is noticeably lighter in color and fluffy.
Add the blueberries to the butter and sugar and cream at a high speed. Make sure the blueberries get “mashed” into the mixture so that they are pureéd and fully combined with the butter and sugar. The mixture should be a deep purple color.
Gradually fold the dry ingredients in with the wet ingredients to form a dough. Mix in the white chocolate chips.
Chill the dough in the freezer for 30 minutes before shaping into 12 balls.
Bake the cookies for 10-13 minutes or until they are slightly brown on the edges. Let cool on a cooling rack for 5-10 minutes.