01 - Whisk together flour, baking powder, and salt in a medium bowl until thoroughly combined. Set aside for later use.
02 - Beat softened butter and granulated sugar with an electric mixer on medium-high speed until light and fluffy, approximately 2-3 minutes. The mixture should appear pale and increased in volume.
03 - Add egg and vanilla extract to the butter mixture. Mix on medium speed until fully incorporated, scraping down the sides of the bowl as needed.
04 - Gradually add dry ingredients to the wet mixture on low speed, mixing just until a smooth dough forms. Avoid overmixing to prevent tough cookies.
05 - Divide dough in half and flatten each portion into a disc. Wrap tightly in plastic wrap and refrigerate for at least 1 hour. Chilled dough prevents spreading during baking.
06 - Preheat oven to 350°F. Line two baking sheets with parchment paper for easy cleanup and to prevent sticking.
07 - On a lightly floured surface, roll one dough disc to 1/4-inch thickness. Cut heart shapes using a cookie cutter and transfer to prepared baking sheets, spacing 1 inch apart.
08 - Gather scraps, re-roll, and cut additional shapes. Repeat with the second dough disc until all dough is used.
09 - Bake for 8-10 minutes until edges are just beginning to turn golden brown. Centers should remain soft. Cool on baking sheet for 5 minutes before transferring to a wire rack.
10 - Whisk powdered sugar, 2 tablespoons milk, and vanilla extract in a small bowl until smooth. Add additional milk 1 teaspoon at a time if needed for desired consistency. Tint with food coloring if desired.
11 - Once cookies are completely cool, spread or drizzle glaze over each cookie. Top immediately with sprinkles or colored sugar. Allow glaze to set for 30 minutes before serving or storing.