Butterscotch Budino

Instructions

1. Combine brown sugar, salt, and water in a deep, heavy-bottomed saucepan and place over medium-high heat. Bring to a boil; cook until caramel is very dark, and bubbles appear, 7 to 10 minutes. Immediately turn off the heat.
2. Carefully whisk in 2 tablespoons butter; pour in heavy cream and continue to stir. Be careful, as mixture may boil up in the pan. Stir over medium-low heat until sugar dissolves. Whisk in milk.
3. Whisk whole egg, egg yolks, and 2 tablespoons plus 1 teaspoon cornstarch together in a mixing bowl. Slowly whisk in 1 cup of hot cream mixture to temper egg mixture. Whisk egg mixture into the saucepan and increase heat to medium-high. Bring to a simmer, and cook, whisking, until mixture thickens, about 2 minutes.
4. Remove from heat and pour into a fine-mesh strainer set over a bowl to remove any lumps. Whisk in rum.
5. Pour into serving glasses. Let cool to room temperature, about 20 minutes, before wrapping in plastic wrap and refrigerating until thoroughly chilled, 3 to 4 hours.