Preheat the oven to 350°F and line baking sheet(s) with parchment.
These cookies can easily be mixed by hand since the butter is melted.
Mix the melted butter and sugar together in a mixing bowl.
Beat in the egg, millk and vanilla.
Add the flour, baking powder and salt and stir to combine.
Stir in half the sprinkles by hand.
Portion about 2 tbsp dough per cookie, roll the top in sprinkles, place on the baking sheet, spaced about 2 inches apart. Gently flatten the top so they are disk shaped.
Bake for 12-14 minutes. They will brown just a little on the bottom. Do not be tempted to over bake if they look a little pale.
Cool 5 minutes on the pan, then transfer to a wire rack to cool completely.
These cookies stay fresh for a week when stored in a sealed container.