01 - In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
02 - In a large bowl, beat the butter and granulated sugar with an electric mixer until light and fluffy, about 2–3 minutes.
03 - Add the egg and vanilla extract, mixing until well combined.
04 - Gradually add the dry ingredients to the wet mixture, mixing on low speed until a smooth dough forms.
05 - Divide the dough in half, flatten each half into a disc, wrap in plastic wrap, and refrigerate for at least 1 hour.
06 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
07 - On a lightly floured surface, roll out one disc of dough to 1/4-inch thickness. Cut out heart shapes using a cookie cutter and transfer to prepared baking sheets.
08 - Repeat with the remaining dough, re-rolling scraps as needed.
09 - Bake for 8–10 minutes, or until the edges are just beginning to turn golden. Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
10 - For the glaze, whisk together powdered sugar, milk, and vanilla extract in a small bowl until smooth. Add food coloring if desired.
11 - Once cookies are completely cool, spread or drizzle glaze over each cookie and decorate with sprinkles. Allow glaze to set before serving.