Take your unsalted butter and egg out of the refrigerator to let them warm to room temperature, about 15-20 minutes.

In a large mixing bowl, cream together the softened butter and granulated sugar with an electric mixer on medium speed until light and fluffy, about 2-3 minutes.

Add in your room-temperature egg and vanilla extract, mixing until blended.

In a separate bowl, whisk together the all-purpose flour and baking powder. Gradually add this to the wet ingredients, mixing gently until just combined.

Wrap the dough in plastic wrap and refrigerate for about 30 minutes.

Preheat your oven to 350°F (175°C) while the dough is chilling.

Roll the chilled dough into small balls, about 1 inch in diameter, and coat each in pastel sanding sugar.

Place the dough balls about 2 inches apart on a parchment-lined baking sheet.

Bake for 10 minutes until edges are set but centers are soft.

Cool for 2 minutes then press a chocolate kiss into the center of each warm cookie.

Transfer cookies to a wire rack to cool completely for about 10-15 minutes.