Prepare the Cookie Dough:

• Preheat your oven to 375°F (190°C) and line baking sheets with parchment paper.
• In a large bowl, cream together butter and sugar until light and fluffy.
• Add the egg and vanilla extract, beating until combined.
• In a separate bowl, whisk together flour, baking powder, and salt. Gradually add to the wet ingredients, mixing until a soft dough forms.

Roll and Cut:

• Roll the dough out on a floured surface to ¼-inch thickness. Use heart-shaped cookie cutters to cut out shapes.
• Place cookies on the prepared baking sheets and bake for 8–10 minutes, or until the edges are lightly golden. Cool completely on a wire rack.

Prepare the Royal Icing:

• In a bowl, mix powdered sugar, meringue powder, and water until smooth. Adjust the water for the desired consistency.
• Divide into bowls and add food coloring for decorating.

Decorate the Cookies:

• Use a piping bag or a Ziploc bag with the corner snipped to outline and flood the cookies with icing.
• Add sprinkles or write messages while the icing is wet. Let the icing set completely before serving or packaging.