In a small saucepan over medium heat, mix together blueberries, sugar, and lemon juice. Heat until the sugar is dissolved and the blueberries have released their juices, stirring occasionally, or about 5 minutes.

In a small bowl, whisk together the cornstarch and water until smooth. Add the cornstarch mixture to the blueberry mixture, stirring constantly. Cook the blueberry filling for an additional 1-2 minutes or until it thickens to your desired consistency.

Remove the blueberry filling from the heat and let it cool slightly while you prepare the cookie dough.

Preheat the oven to 350°F and line a baking sheet with parchment paper.

In a medium bowl, whisk together the flour, baking powder, salt, and baking soda. Set aside.

In a stand mixer fitted with the paddle attachment, cream together the butter and granulated sugar on medium speed until light and fluffy, about 2 minutes. Add the eggs, milk, and vanilla and continue mixing until combined. Stop to scrape down the sides of the bowl as needed.

Reduce the mixer speed to low and add the flour mixture. Mix until all ingredients are just incorporated.

Mix in blueberries.

In a small bowl, mix together the flour, granulated sugar, brown sugar, lemon zest, salt, and melted butter until crumbly. Set aside.

Spread about half of the blueberry filling over the top of the cookie dough in the bowl.

Without mixing it in, use a 1 ½ tablespoon scoop to scoop out 8 cookies onto the lined baking sheet.

To the remaining cookie dough in the bowl, spread the rest of the blueberry filling over the top. Scoop out the remaining cookie dough onto the baking sheet. (You should have about 16 cookies total.)

Top each cookie with a spoonful of crumble, gently pressing the crumble into the dough.

Bake for 14-16 minutes, or until the edges are set and lightly browned. The centers should be soft.

Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. Enjoy!