Heat the oven to 300°. Place the half-and-half and espresso in a pot. Open the vanilla bean, scrape the seeds into the pot, toss in the pod and heat the pot over medium heat. Meanwhile, whip the yolks, eggs, sugar and extract until pale and fluffy.
When the dairy mixture comes to a simmer, remove from the heat and, carefully and quickly whisk 1 cup of the dairy mixture into the egg mixture--whisking constantly until incorporated. Add the rest of the dairy mixture to the egg mixture and mix well then strain and divide the mixture into 6 4-oz. ramekins.
Place the ramekins into a high-sided roasting pan. Fill the pan with boiling water halfway up the sides of the ramekins and bake until just set—about 25 to 30 minutes. Let cool, then chill until ready to serve.