2 envelopes unflavored gelatin, softened in ¼ c. cold water
Scald milk in top of double boiler. Mix sugar, flour and salt and add a little of the hot milk. Blend well and add to milk in double boiler. Cook over boiling water until bubbles form at the edge of the pan.
Remove from heat. Add the hot mixture gradually to the eggs. Return to double boiler and cook over simmering, not boiling, water, stirring constantly, until mixture coats a wooden spoon.
Remove from the heat; gradually stir the hot mixture into the gelatin, stirring until the gelatin completely dissolves. Refrigerate until custard thickens, about 2 hours, or until it reaches 70°. (You can cook the custard a day ahead and refrigerate it.) Add vanilla to cooled custard.