In a heavy-bottomed 2 quart saucepan, heat cream, milk, sugar and vanilla bean. (If you are using vanilla extract, do not add it until later.) Stir occasionally until sugar is disolved and the mixture is hot but not boiling.

Whisk egg yolks together in a bowl. Continue whisking and very slowly pour in approximately 1 cup of the cream mixture. When smooth, pour back into the pan.

Whisk constantly over low heat until the mixture thickens slightly and coats the back of a spoon (about 5 minutes).

Take care that the mixture doesn't boil, or it will curdle. Draw your finger across the back of the coated spoon. If the line you make remains, the custard is done. Remove vanilla beans; or if you're using vanilla extract, add it now. Makes 8 servings.