'Funny Face' biscuits

I want to make some funny face biscuits (y'know the plain shop bought biscuits with homemade icing and decorations).

Just wondering if anyone knows the best icing mixture to use for these? I will be wanting to make them the day before. Thanks :)

royal icing or buttercream...

royal is the one that sets hard (icing sugar and egg white/meringue powder)

buttercream will "crust" but still be soft in the middle, its just butter and icing sugar and whatever flavour flavours/colours you want to add.

The icing sugar, butter, water is easy and if you want children to ice them they can easily spread the icing.

To make it really easy, I get the Betty Crocker frosting in the tub which is in the cake aisle :). If you get the vanilla one you can then scoop spoonfuls out into little bowls and add colouring so you can then have a few different colours for the kids to choose from.

I just use icing sugar and water as its really easy and sets hard, esp if you're going to do them the night before. If I add butter, its still soft in the middle and I inevitably stick my fingers in them when taking them out of the container, lol!