I will probably do cookies using the rolled buttercream/marshmallow fondant combo, they will need to be bagged so would it be better to use royal icing or glacé? The royal will probably break down but be easier for me to use with small details, will glacé do the same (break down from the fat in the rolled icing)? TIA

I am not positive, but I Think I remember reading a while back that the RI will break down if there is any fat while it's being mixed, but that it will be OK if it is already completely mixed.

But, please - don't hold me to that! I've never tried it! Maybe someone who knows more than me can chime in...

I'm pretty sure it did when I used it a few years ago on RBC, I was just looking to see about what everyone thought and if the glacé would hold up. . .guess I'll find out!