While the red icing on the heart cookies is hardening, decorate the XO cookies.
Pour gold sugar crystals on a small plate. Set aside.
Continue using the pastry bag with the 1/2 white piping icing that we used on the diamond ring sugar cookies.
Outline each 'X' and 'O' cookie with white icing. Set the 'O' cookies aside until further noted below.
Next, cut the end of the pastry bag to make the hole a bit bigger (this will make it easier to flood each cookie with piping icing).
Flood the 'X' cookie with icing.
Place the cookie face down on a plate of sugar crystals.
Remove the cookie from the sugar crystals.
Lightly tap the cookie to remove any excess sugar crystals.
Set cookie aside and repeat this step with the remaining 'X' cookies.
Flood the 'O' cookie with icing.
Place the cookie face down on a plate of sugar crystals.
Remove the cookie from the sugar crystals.
Lightly tap the cookie to remove any excess sugar crystals.
Set cookie aside and repeat this step with the remaining 'O' cookies.