01 - In a medium mixing bowl, thoroughly whisk together the all-purpose flour, baking powder, and salt. Set this mixture aside.
02 - In a large mixing bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until the mixture becomes light and fluffy, which typically takes 2 to 3 minutes.
03 - Add the large egg and pure vanilla extract to the creamed butter mixture. Continue to beat with the electric mixer until all ingredients are well combined.
04 - Gradually incorporate the reserved dry ingredients into the wet mixture. Mix on a low speed until a soft, cohesive dough forms.
05 - Divide the prepared dough into two equal portions. Gently flatten each portion into a disc, wrap tightly in plastic film, and refrigerate for a minimum of 1 hour to allow the dough to firm up.
06 - Preheat your oven to 350°F. Line several baking sheets with parchment paper to prevent sticking.
07 - On a lightly floured surface, take one chilled dough disc and roll it out evenly to a thickness of approximately 1/4 inch. Use a heart-shaped cookie cutter to cut out individual cookies.
08 - Carefully transfer the cut-out cookies to the prepared baking sheets, ensuring they are spaced about 1 inch apart. Bake for 8 to 10 minutes, or until the edges of the cookies are just lightly golden.
09 - Allow the baked cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely. Ensure cookies are fully cooled before decorating.
10 - In a clean bowl, whisk together the sifted powdered sugar, milk, light corn syrup, and pure vanilla extract until the mixture is smooth and free of lumps. Adjust the consistency by adding more milk a teaspoon at a time if the icing is too thick.
11 - Divide the prepared icing into separate bowls. Tint each bowl of icing with food coloring of your choice until desired shades are achieved.
12 - Decorate the completely cooled cookies using the tinted icing. Apply icing with a piping bag, a squeeze bottle, or a small spoon. Allow the icing to set and harden before serving or storing the cookies.