1/2 vanilla bean, split lengthwise
1 cup whole milk
1 cup heavy cream
2/3 cup Guinness stout
2 tablespoons plus 2 teaspoons molasses
4 egg yolks
1/3 cup sugar
1/2 teaspoon vanilla extract
1. In a medium saucepan, scrape in the vanilla bean seeds. Add the pod, milk, and cream. Bring to a boil over medium heat. Turn off the heat, cover the pan, and let the flavors infuse for 30 minutes.
2. Meanwhile, in a small saucepan over medium-high heat, whisk together the stout and molasses. Bring to a boil and turn off heat.
3. In a large mixing bowl, whisk the yolks, sugar, and vanilla extract. Whisk in a few tablespoons of the hot cream mixture, then slowly whisk in another 1/4 cup of the cream. Add the remaining cream in a steady stream, whisking constantly. Pour the mixture back into the saucepan.
4. Stir the beer mixture into the cream mixture. Cook the custard over medium heat, stirring often with a wooden spoon, for 6 to 8 minutes or until the custard thickens enough to coat the back of the spoon.
5. Strain the mixture into a bowl and refrigerate for at least 2 hours or overnight. Process the custard in an ice cream maker according to the manufacturer's instructions.