Mix the cornstarch with a little cold water, and stir in half a cupful of boiling water. Beat the sugar, eggs and lemon together, and stir into the boiling corn-starch. Place the basin in another of boiling water, and stir (over the fire) until it thickens, perhaps from eight to ten minutes; then add the butter and set away to cool. Line little patty pans with puff paste, or any rich paste, rolled very thin. Put a spoonful of the mixture in each one, and bake in a slow oven from twelve to twenty minutes. When cool, slip out of the pans, and serve on a napkin. They are nice for lunch, tea or children's parties, only for parties make them small. The mixture for fanchonettes will keep a number of weeks in a cool place, so that if one makes a quantity at one time, portions can be used with the trimmings of pastry left from pies.