For the life of me I cannot figure out why Elizabeth Bard says to put these in tall glasses.
Personally, I have some little mini trifle bowls that would have been perfect for these. In fact, in Lunch in Paris she writes that these are based on a Nigella Lawson recipe from Nigella Bites. Of course I happen to have a copy of that lying around. Sure enough, NL says ramekins, or maybe even a styrofoam cup. Maybe EB likes the anticipation of having to dig it out of the bottom of said tall glass.
Either way, a lovely little treat that can be made ahead.
Eat Well and Savor.