In a large heavy saucepan, combine the first five ingredients. Stir in milk until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat to low; cook and stir 2 minutes longer. Remove from the heat.

Stir a small amount of hot mixture into the egg yolks; return all to the pan. Bring to a gentle boil, stirring constantly; cook 2 minutes or until mixture is thickened and coats the back of a spoon. Remove from the heat.

Stir in butter and vanilla. Cool for 15 minutes, stirring occasionally. Transfer to six dessert dishes. Cover and refrigerate until chilled. Garnish with whipped cream if desired. Yield: 6 servings.