01 - In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
02 - In a large bowl, beat butter and sugar with an electric mixer until light and fluffy (2–3 minutes).
03 - Add egg and vanilla extract; beat until combined.
04 - Gradually add the dry ingredients, mixing on low speed until a soft dough forms.
05 - Divide dough in half, flatten into discs, wrap in plastic, and refrigerate for at least 1 hour.
06 - Preheat oven to 350°F. Line 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.
08 - Place cookies 1 inch apart on prepared baking sheets.
09 - Bake for 8–10 minutes, until edges are just golden. Cool on the sheet for 5 minutes, then transfer to a wire rack to cool completely.
10 - For the icing, whisk powdered sugar, milk, corn syrup, and vanilla until smooth. Adjust consistency with milk if needed.
11 - Divide icing among bowls and tint with food coloring as desired.
12 - Decorate cooled cookies with icing using a piping bag, squeeze bottle, or spoon. Let icing set before serving or packaging.