Preheat oven to 300°F.
Heat cream, milk and sugar in a saucepan until almost boiling.
In a separate bowl beat whole eggs and extra egg yolks together well.
Gradually whisk the heated mixture into the eggs then return mixture to the saucepan. Cook over moderate heat, stirring constantly with a wooden spoon, until the custard coats the back of a spoon, 3-4 minutes. Remove from heat.
Stir in vanilla.
Pour custard into 6-8 individual custard dishes or into 1 shallow 9-inch baking dish.
Set dishes in a large baking pan and put in the oven. Pour boiling water into the outer pan to come almost all the way up the sides of the ramekins.
Bake for 35 minutes for shallow dishes, 40 minutes for deeper ramekins, until the center of the custard is set. When done, remove custard from water bath and cool. Cover and chill.