In a medium bowl, whisk together flour, baking powder, salt, and instant espresso powder.

In a large bowl, beat butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.

Add egg and vanilla extract to the creamed mixture and mix until fully incorporated.

Gradually add dry mixture to wet ingredients, mixing just until combined.

Cover the dough and refrigerate for at least 30 minutes.

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

Scoop dough into 2-tablespoon portions and roll into balls. Place on the baking sheet.

Bake cookies for 10-12 minutes until edges are set and centers are slightly soft.

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

Whisk together powdered sugar, milk, and optional espresso powder to make the glaze.

Drizzle glaze over cooled cookies and allow to set for 15-20 minutes.