Step 1

Preheat oven to 450°F. Coat 6 (1-cup) ramekins with cooking spray.

Step 2

Melt butterscotch chips and butter in a small saucepan over medium, stirring constantly, until smooth, about 2 minutes. Remove from heat; whisk in 3 tablespoons of the bourbon and 1 teaspoon of the vanilla. Transfer mixture to a medium bowl, and whisk in 1 cup of the powdered sugar until smooth. Whisk in egg yolks and eggs. Fold in flour and salt using a rubber spatula until fully combined.

Step 3

Spoon batter evenly into prepared ramekins (about ⅓ cup each). Arrange ramekins on a baking sheet. Bake in preheated oven until cake tops are golden brown and centers have a slight jiggle, 10 to 11 minutes.

Step 4

Meanwhile, beat cream and remaining 2 tablespoons powdered sugar, 1 tablespoon bourbon, and 1 teaspoon vanilla with an electric mixer on medium-high speed until stiff peaks form, about 2 minutes. Set aside.

Step 5

Remove cakes from oven, and let stand 1 minute. Gently run an offset spatula or a sharp knife around edges of each cake, and carefully invert each onto a serving plate. (Use a kitchen towel or oven mitt to prevent burning.) Sprinkle cakes with additional powdered sugar, and dollop evenly with bourbon whipped cream before serving.