Preheat oven to 350°F (175°C). Cream together softened butter and granulated sugar until light and fluffy.

Add eggs one at a time, mixing well after each addition, then stir in vanilla extract.

Gradually mix in flour until fully combined; knead dough if crumbly.

Roll out dough on a floured surface to about ¼ inch thick; cut into heart shapes.

Place cookies on an ungreased baking sheet and bake for 8-10 minutes until edges are golden. Cool completely on racks.

For royal icing, mix powdered sugar with egg whites (or meringue powder) and water until stiff peaks form.

Divide into portions for coloring if desired.

Decorate cooled cookies using piping bags or squeeze bottles.