Bake 8 to 10 minutes or until light brown on bottom. Cool 2 minutes; remove from cookie sheets to cooling racks. Cool completely. In medium bowl, stir together 3 tablespoons butter, the powdered sugar and vanilla. Stir in milk, 1 tablespoon at a time, until smooth and consistency of thick syrup. Drizzle over cookies; let stand until set. To store, place waxed paper between cookie layers. Store in airtight container.