Combine butter and sugar in a mixing bowl and beat until soft and fluffy

In a separate bowl, combine flour, baking powder, salt, and sprinkles, and set aside

Add egg to the butter and sugar mixture and beat till combined.

Slowly add in the dry ingredients and mix till fully incorporated.

Form dough into two logs and wrap in plastic and refrigerate at least 2-4 hours.

Preheat oven to 350 and line baking sheet with silpat or parchment paper.

Once chilled, remove one log from the fridge at a time and slice into round slices of dough.

Roll each slice out slightly, and pinch three corners to form a triangle, rolling sides up to form an opening in the center of the triangle.

Bake until bottoms of cookies are a light golden brown.

Remove from oven and cool completely before icing.

Put all ingredients except sprinkles in a mixing bowl and beat until icing is a desired consistency.

Add sprinkles and mix in.

Spread into the open space in the center of the cookie.