Make Ahead: The pudding needs to be chilled overnight. It can be refrigerated up to 2 days in advance. The whipped cream and butterscotch sauce can be refrigerated up to 3 days in advance; you’ll probably have some sauce left over.
Ingredients
FOR THE PUDDING
8 tablespoons (1 stick) unsalted butter, at room temperature
1 cup packed light brown sugar
Scant 1/2 teaspoon kosher salt
2 cups heavy whipping cream
1 1/2 cups whole milk
2 large eggs
Heaping 1 1/2 teaspoons arrowroot powder
1 tablespoon plus 1 teaspoon light rum
1 tablespoon good-quality vanilla extract
FOR THE SAUCE
6 tablespoons dark corn syrup
1/2 teaspoon kosher salt
1 cup granulated sugar
1 cup heavy whipping cream
1 cup packed light brown sugar
3 tablespoons unsalted butter
1 1/2 tablespoons good-quality vanilla extract
FOR THE WHIPPED CREAM
1 cup chilled heavy whipping cream
Confectioners’ sugar
1 teaspoon good-quality vanilla extract
Instructions
For the pudding: Combine 4 tablespoons of the butter, the light brown sugar and salt in a heavy pot over medium heat. Cook for a few minutes, whisking constantly, until homogenous. Gradually add 1 cup of the heavy whipping cream; cook for about 5 minutes, whisking constantly, until the mixture has reduced by half. Remove from the heat, then whisk in 3/4 cup of the milk until well blended.
Whisk together the eggs, the remaining 3/4 cup milk, the arrowroot powder and the remaining cup of heavy whipping cream in a liquid measuring cup, then gradually whisk it into the cooked-sugar mixture until well incorporated. Return the pot to the stove over low heat; cook just until the mixture begins to thicken, stirring as needed. Remove from the heat.
Combine the remaining 4 tablespoons of butter, the rum and vanilla extract in a deep bowl. Place a fine-mesh strainer over the top; pour in the pudding mixture, using a spatula to push it through. Use an immersion (stick) blender to puree until creamy and somewhat lightened. Transfer to a shallow baking dish, cover with plastic wrap directly on the surface and refrigerate overnight.
For the sauce: Combine the dark corn syrup, salt, granulated sugar, heavy whipping cream, light brown sugar and unsalted butter in a heavy pot over medium heat. Cook for 10 minutes, stirring, until thoroughly blended. Remove from the heat.
Stir in the vanilla extract until well blended, then strain through a fine-mesh strainer into a heatproof container. Cool, cover and refrigerate until ready to serve. The yield is about 1 1/2 cups.
For the whipped cream: Combine the heavy whipping cream, a few tablespoons of confectioners’ sugar (to taste) and the vanilla extract in the bowl of a stand mixer or handheld electric mixer; beat on medium-high speed until soft peaks form. Cover and refrigerate until ready to serve.
When ready to assemble, drizzle some sauce inside dessert glasses or bowls. Divide the pudding among them evenly, then top with the whipped cream and another drizzle of sauce. Serve right away.