1. Preheat the oven to 350°F and line two baking sheets with parchment paper.

2. Make the streusel by mixing the flour, brown sugar, cinnamon, and melted butter in a small bowl until crumbs form. Set aside.

3. In a large bowl, beat the softened butter, brown sugar, and granulated sugar until light and fluffy.

4. Add the eggs and vanilla extract, then mix until smooth.

5. In a separate bowl, whisk together the flour, baking powder, salt, and cinnamon.

6. Gradually add the dry ingredients to the wet ingredients and mix just until a soft dough forms.

7. Scoop the dough into balls and place them on the prepared baking sheets, leaving space between each cookie.

8. Top each cookie with a generous spoonful of streusel and lightly press it into the dough.

9. Bake for 11 to 13 minutes, until the edges are set and the tops look lightly golden.

10. Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack.

11. Whisk together the powdered sugar, milk, and vanilla extract to make the glaze.

12. Drizzle the glaze over the cooled cookies and serve.