1. Prepare the Blueberry Mixture

• In a small saucepan over medium heat, cook the blueberries for about 5 minutes until they break down and release their juices.
• Mash them slightly with a fork and let them cool completely.

2. Make the Cookie Dough

• In a large bowl, cream together the butter and granulated sugar until light and fluffy.
• Mix in the egg and vanilla extract until fully incorporated.
• Stir in the cooled blueberry puree, ensuring it is evenly distributed.

3. Combine Dry Ingredients

• In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
• Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
• Cover the dough and refrigerate for at least 1 hour (this helps with the crinkle effect).

4. Form and Coat the Cookies

• Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
• Scoop out tablespoon-sized portions of dough and roll them into balls.
• Generously coat each ball in powdered sugar, ensuring full coverage.

5. Bake

• Place the dough balls on the prepared baking sheet, spacing them about 2 inches apart.
• Bake for 12–14 minutes, or until the cookies are set and have a cracked surface.
• Let them cool on the baking sheet for 5 minutes before transferring to a wire rack.