Make the crêpes.
Mash together the white cheese, the butter, the seasonings, and the egg, then briskly stir in the spinach until well mixed but still mottled in appearance. Add the Parmesan progressively, stirring and mashing after each addition, until a firm paste is formed. Stuff each crêpe with a couple of mounded tablespoonsful of the mixture, rolling it like a cannelloni into the form of a thick cigar, and arrange them, flap side down, in a buttered gratin dish just large enough to hold them placed loosely side by side without packing. Sprinkle Parmesan over the surface, place a long thin strip of butter on each crêpe, and bake in a 450° oven for from 20 to 25 minutes or until swelled and golden brown.