I would like to try Toba's glace.
Should I keep the cookies in the fridge or I can leave them out?
Definitely leave them out, at least until the icing has fully set (a minimum of 24 hours). This icing does not like getting cold, and will spot and get funky looking. Adding brite white to the icing helps....some. The high sugar content acts as a preservative, so you don't have to worry about spoiling (even when made with milk).
Thank you very much!!!!!