Whisk together the egg yolks and 1/2 cup sugar in a medium mixing bowl until smooth and creamy. Add cream and vanilla and gently stir to combine, taking care not to mix quickly so as not to introduce extra bubbles. Place un-filled ramekins in a baking or casserole dish and fill baking dish with hot water until about half-way up sides of ramekins. Pour egg mixture into ramekins.
As written, this recipe works best for shallow ramekins. Deeper ramekins will require longer cooking times in order to set.