Preheat oven to 350 degrees Fahrenheit.
Place washed blueberries in a saucepan and cook over medium heat. Use a fork or potato masher to smash the blueberries. Continue to cook while stirring until blueberry sauce is slightly thickened. Remove from heat and allow to cool.
White the blueberry sauce is cooling, whip the softened butter with a hand or stand mixer until light and fluffy.
Add the brown and white sugars and whip again.
Make sure that the blueberry sauce is cooled off, then add it to the butter mixture and whip until fully combined.
Add the baking powder and salt and mix them in.
Add 1 1/2 cups of flour and mix until incorporated.
Add the remaining 1 1/2 cups flour and mix thoroughly.
Add the white chocolate chips or almond bark and fold them in with a spatula.
Using a 1 Tbsp. cookie scoop, scoop dough onto a baking sheet lined with a silicone baking mat, or lightly greased.
Bake cookies for 10 to 12 minutes until lightly browned and set.
Allow to cool for 5 minutes.
Store in an airtight container at room temperature for 3 to 5 days.