Make the crÉpe batter 2 hours in advance. Right before making the crÉpe, thin the batter with a little cold water if thickened. Fry the crÉpes in butter. They can be made the day before. Chop the mushrooms. Fry them gently in 2 tablespoons of butter. When all of their water has evaporated, remove from the heat and add 1 tablespoon of cream and 1 or 2 tablespoons of grated cheese. Taste before you salt and pepper. Put a slice of ham onto each crÉpe. Generously spread with mushrooms then roll. Put the crÉpes, one by one, into a gratin dish. Sprinkle with lightly salted and peppered cream. Cover with GruyÅre cheese. Bake at 350F. Gratin.
