Whisk flour, baking powder, and salt; set aside.

Beat butter and sugar until light, about 2–3 minutes.

Add egg and vanilla; mix until combined.

Gradually add dry ingredients; mix to form a stiff dough. Add 1 tbsp milk only if too crumbly.

Scoop dough (1 tbsp) and roll into balls; place 2 inches apart on baking sheets.

Use the bottom of a glass to gently flatten to 1/4-inch thickness.

Bake at 350°F (175°C) for 8–10 minutes, until edges set but centers remain pale. Cool on racks before decorating.