Place the half-and-half in a medium saucepan. Split the vanilla bean in half lengthwise with a small knife to loosen the seeds, then place in the pot with the pod. Heat the half and half over medium heat until it just begins to simmer. Remove from the heat and discard the vanilla bean. Add the bittersweet chocolate, semisweet chocolate, and sugar and stir until the chocolate melts and the sugar dissolves.
In a large bowl, whisk together the egg yolks, salt, and liqueur. Gradually add the chocolate mixture to the bowl with the egg mixture, whisking constantly, until the mixture is smooth.
Put 10 to 12 jelly jars or 4-ounce ramekins in a shallow baking dish and fill the dish with warm water about halfway up. Pour the chocolate mixture into the jars or ramekins, dividing it evenly among them.
Bake until firm around the edges but still slightly loose in the center, 30 to 35 minutes. Remove from the oven and carefully take the pots de creme out of the water and set aside to cool to room temperature. Cover and refrigerate to chill for at least 2 hours or up to 2 days. Remove from the refrigerator for 1 hour before serving.