Cookie Dough

1. Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. In a large bowl, cream together the softened butter and packed brown sugar until light and fluffy, about 2 minutes.
3. Beat in the egg and vanilla extract until smooth and fully combined.
4. In a small bowl, whisk together flour, cinnamon, salt, and baking powder. Add this to the butter mixture, mixing just until combined and a dough forms.
5. Roll the dough into balls (about 1.5 inches), press down slightly into a small disc and place on a lined baking sheet, leaving some space between each cookie.

Streusel

1. In a small bowl, combine cold butter cubes, brown sugar, flour, and cinnamon. Use a fork or your fingers to crumble the mixture together until it resembles coarse crumbs.
2. Lightly press a spoonful of streusel onto each cookie, pressing gently so it adheres.

Bake

1. Bake for 12-15 minutes, or until the edges are lightly golden. Let cool on the baking sheet for 5 minutes, then transfer to a wire rack.

Icing

1. In a bowl, whisk together powdered sugar, milk, pumpkin spice, and cinnamon until smooth.
2. Once the cookies are completely cool, drizzle the icing over them. Let the icing set for a few minutes before serving.