Soften the gelatin in cold water. Combine the ½ cup sugar with the salt, egg yolks, and milk in the top of a double boiler. Cook over boiling water, stirring constantly, until mixture coats a spoon.
Remove from heat and stir in softened gelatin and pawpaw puree. Chill until a spoonful holds its shape (about half an hour).
Beat the egg whites stiff with ¼ cup of white sugar. Fold the egg whites and half of the whipped cream into the filling. Pour into the baked pastry shell. Spread remaining whipped cream on top of the pie.