In a large mixing bowl, whisk together all-purpose flour, baking powder, and salt until combined. In a separate bowl, cream together unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes. Mix in the egg, vanilla extract, and milk until fully incorporated. Gradually add the dry ingredients, stirring until a soft dough forms.

Scoop tablespoon-sized portions of the chilled dough and roll them into balls using your hands. Roll each ball in powdered sugar until completely coated. Place the coated dough balls on a parchment-lined baking sheet, leaving space between them.

Preheat your oven to 350°F (175°C). Bake the cookies for 10-12 minutes, or until the edges are set and the tops have formed their signature crinkles.

While the cookies are still warm, gently press the back of a teaspoon into the center of each cookie to create a small well.

In a mixing bowl, whip together mascarpone cheese, heavy cream, powdered sugar, and espresso powder until smooth and creamy. Avoid overmixing.

Once cooled, spoon or pipe the mascarpone filling into the center of each cookie wells. Dust the tops with cocoa powder before serving.