A must for this recipe is pure maple syrup.
Dissolve the gelatin in the water. Put the milk in a double boiler and sprinkle the dissolved gelatin on top. Heat to scalding, stirring until gelatin dissolves entirely.
Beat the egg yolks with salt, stirring in half the milk slowly. Return all to the double boiler and cook over hot (not boiling) water until the mixture coats the spoon.
Remove from the heat, stir in the maple syrup, and cool until the mixture thickens. Then whip until light and frothy. Beat the egg whites stiff, and fold into the syrup and egg mixture. Chill until firm.