Preheat the oven to 350 F. Add the butter and brown sugar to a bowl. Mix for 2-3 minutes. Add the greek yogurt, eggs, and vanilla extract and mix again.
Add flour, cornstarch, baking soda, and salt. Mix until flour is just combined. Add dried blueberries and fold in until just combined. Cover the bowl and chill the dough in the fridge while you make the streusel.
To make the streusel add the butter, brown sugar, and flour to a bowl. Mix until combined. Transfer to a baking sheet or glass pan. Press the mixture down in the center of the pan, spreading the dough until its 1/2 inch thick.
Transfer to the oven and bake for 10 minutes. Remove and use a fork to break up the dough -- the streusel will still be soft but starting to cook, so it should start to break up into pieces. Transfer back to the oven and cook an additional 5 minutes. Remove and let the streusel cool completely (you can also put it in the fridge to speed up the cooling process).
Remove the dough from the fridge. Use a large cookie scoop (about 1/4 cup) to scoop out the dough. Press each dough ball into the streusel, ensuring that plenty of streusel sticks to the top.
Place up to 6 cookies on a lined or greased baking sheet. Bake for 11-13 minutes, until cookies are just starting to brown. Let them cool on the baking sheet for 5 minutes then transfer to a cooling rack.
Enjoy! Keep any extra cookies in a sealable container.
