Preheat oven to 350°. Line two large baking sheets with parchment paper, or non stick spray. Set aside.
In a small bowl, whisk together flour, cornstarch, salt and baking powder. Set aside.
In a large bowl of stand mixer or handheld mixer, cream together butter and sugar on high speed for about 2 minutes.
Add egg and vanilla extract. Mix until well combined.
Turn mixer down to low, and add in dry ingredients. Mix to combine.
Fold in about 3/4 of white chocolate chunks, reserving some to top on the cookies.
Carefully, fold in blueberries using a spatula. Be gentle so you don't crush them all. Its ok to crush a few!
In a small bowl mix together ingredients for filling: cream cheese, vanilla and powdered sugar until well combined.
To make cookies, scoop a tablespoon of dough and shape it into a bowl, with a deep center (for the filling).
Fill the center with 1 teaspoon of cream cheese filling, followed by 1/2 teaspoon of blueberry jam.
Top with 1 teaspoon of dough, seal any openings and roll into a ball. Place cookies on baking sheet, making sure to spread out enough. I fit 5 cookies on each baking sheet. They spread a bit while baking.
Repeat until you use up all dough. Press a few white chocolate chunks on top of cookie dough balls.
Bake in preheated oven for 16-18 minutes. Enjoy!
