Prep time: 15 minutes
Total time: 1 hour, plus overnight freezing
for the frozen vanilla custard:
5 large egg yolks
1/2 cup granulated sugar
1 1/2 cups heavy cream
1 1/2 cups whole milk
pinch of kosher salt
1 teaspoon good quality pure vanilla extract
for the hot fudge sauce:
1/3 cup heavy cream
2/3 cup whole milk
¼ cup granulated sugar
2 tablespoons unsalted butter
1 cup bittersweet chocolate, finely chopped
1. Make the frozen custard: Put the egg yolks and sugar into a heavy medium saucepan and whisk until smooth. Whisk in the cream and milk. Cook over medium heat, stirring frequently with a wooden spoon, until the custard reaches a temperature of 170°F on an instant-read thermometer or is thick enough to coat the back of the spoon.
2. Strain the custard into a medium bowl. Stir in the salt and vanilla. Set that bowl into a larger bowl filled with ice, then stir the custard frequently until it has cooled. Cover the custard and refrigerate it until completely chilled, about 4 hours.
3. Churn the custard in an ice maker following the manufacturer's instruction. Scoop the custard into a quart container with a lid, cover, and store in the freezer for at least 2 hours, until firm. Custard can be kept up to a month in the freezer, but we prefer to eat it within 24 hours.
4. Make the hot fudge sauce: Put cream, milk, sugar, and butter into a large saucepan and bring just to a boil over medium heat. Add chocolate and cook, stirring often, until chocolate melts. Remove pan from heat. Let fudge sauce cool, stirring occasionally. Fudge sauce will keep, covered and refrigerated, for up to 1 week.
5. Throw the custard and the fudge sauce in a blender and purée until smooth. Add in some other things if you like, like cookies or cake. Embrace your inner fat kid.
AUTHOR'S NOTE: This recipe is reprinted with permission of the author from the book Shake Shack: Recipes and Stories.