01 - Preheat your oven to 350°F. Line two baking sheets with parchment paper to prevent sticking and ensure easy cleanup.
02 - In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer on medium-high speed until the mixture becomes pale, light, and fluffy—about 3 to 4 minutes.
03 - Add the egg and vanilla extract to the butter mixture. Beat on medium speed until thoroughly combined and the mixture looks smooth and glossy.
04 - In a separate medium bowl, sift together the all-purpose flour, salt, and baking powder to ensure even distribution.
05 - Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed just until the flour disappears. Avoid overmixing to keep cookies tender.
06 - Sop about 1 tablespoon of dough and roll between your palms to form smooth balls. Roll each ball generously in pastel sprinkles or colored sanding sugar until evenly coated.
07 - Place the coated dough balls on the prepared baking sheets, spacing them about 2 inches apart to allow for spreading during baking.
08 - Bake for 8 to 10 minutes, watching carefully. The cookies are done when the edges are set and slightly golden but the centers still look soft and underbaked.
09 - Remove the baking sheets from the oven immediately. Gently press a chocolate kiss into the center of each warm cookie while they're still soft—the candy should sink slightly but remain visible on top.
10 - Let the cookies rest on the baking sheet for 5 minutes to firm up slightly. Using a spatula, transfer them to a wire rack to cool completely before serving or storing.