Combine first 3 ingredients in a large saucepan; stir well. Cook over medium-low heat until thoroughly heated (do not boil). Combine eggs and sugar in a medium bowl; stir with a wire whisk until well blended. Gradually stir about one-fourth of hot mixture into egg mixture; add to remaining hot mixture, stirring constantly. Cook mixture over low heat, stirring constantly, 20 minutes or until mixture is slightly thickened and reaches 160°.
Remove mixture from heat; stir in bourbon and 1/4 teaspoon nutmeg. Let cool. Cover and chill 3 hours. Remove and discard vanilla bean; stir in ice cream just before serving. If desired, top each serving with sweetened whipped cream and sprinkle with nutmeg.