Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

In large bowl, cream together softened butter and sugar until light and fluffy.

Beat in egg and vanilla extract until fully incorporated.

Whisk together flour and baking powder in separate bowl, then gradually mix into wet ingredients.

Fold in Valentine sprinkles until evenly distributed through dough.

Scoop dough by tablespoonfuls and roll into balls. Place 2 inches apart on prepared baking sheets.

Make thumbprint indentation in center of each cookie ball using your thumb or teaspoon.

Bake 10-12 minutes until edges barely golden. Cool on baking sheets 5 minutes before transferring to rack.

Melt candy melts in separate microwave-safe bowls (30-second intervals, stirring between each).

Fill cooled cookie indentations with alternating pink and red candy melts using piping bag or spoon.

Immediately decorate with Valentine sprinkles before chocolate sets. Let harden completely before serving.