Combine all ingredients in a large Dutch oven; beat with a wire whisk until well blended. Cook over medium-low heat, stirring constantly, 20 minutes or until mixture thickens and coats a metal spoon. Remove from heat, and cool slightly.
Pour mixture into freezer can of a 1-gallon hand-turned or electric freezer. Freeze according to manufacturer's instructions. Let custard ripen at least 1 hour before serving.
Note: Additional milk may be added to freezer can if mixture does not reach fill line.