In a medium bowl, combine 1/2 cup of all-purpose flour, 1/4 cup of granulated sugar, and 1/2 teaspoon of cinnamon. Mix well to combine.

Add 1/4 cup of cold, cubed unsalted butter to the flour mixture. Using a pastry cutter or your fingers, work the butter into the dry ingredients until the mixture resembles coarse crumbs.

Set the streusel topping aside to chill while you prepare the cookie dough.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, cream together 1 cup of softened unsalted butter, 3/4 cup of granulated sugar, and 3/4 cup of packed brown sugar until light and fluffy. This process incorporates air into the mixture, helping the cookies rise.

Add 2 large eggs, one at a time, mixing well after each addition. Then stir in 1 teaspoon of vanilla extract.

In a separate bowl, whisk together 2 cups of sifted all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, and 1/2 teaspoon of salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can lead to tough cookies.

Gently fold in 1 cup of fresh blueberries, being careful not to crush them.

Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Sprinkle the prepared streusel topping generously over each cookie dough ball.

Bake in the preheated oven for 12-15 minutes, or until the edges are lightly golden and the centers are set. The cookies will continue to firm up as they cool.

Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a cooling rack to cool completely.