Step 1

Soften gelatin in 1/4 cup cold milk.

Step 2

Add 1/2 cup hot milk and stir until gelatin is dissolved.

Step 3

Beat egg yolk lightly with vinegar, salt, mustard, and hot pepper sauce.

Step 4

Stir into milk mixture.

Step 5

Chill until mixture begins to thicken, then whip with a rotary beater. Store in refrigerator.