Glaze icing?

Hi :) I am decorating some shortbread cookies and need to ice them, but the icing needs to set hard. Is that called a glaze? How do I go about it?

You want Royal Icing.

You can find recipes online, or you can buy a bag you mix with water from the supermarket.

Glaze is more for donuts. It's shiny and hard but soft.

You can buy royal icing mixes or make the original recipe with egg whites and icing sugar.

I cheat and use meringue powder as I know it's safe for people who can't do uncooked egg. And I cheat again by using pavlova egg as meringue powder as meringue powder is ridiculously expensive and is the lesser of two evils when it comes to additives.

Thanks ladies! I need to be able to pack them in gift boxes so they can't be sticky. I will look into the royal icing :)