Instructions

• Preheat the oven to 350°F (180°C). Grease and lightly flour three 8-inch round cake pans; line bottoms with parchment if desired. Set pans aside.
• In a medium bowl, whisk together 2 ¾ cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon baking soda, and ½ teaspoon salt. Set aside.
• In a large bowl (or the bowl of a stand mixer fitted with the paddle), cream together 1 cup unsalted butter (softened), 1 cup light brown sugar (lightly packed), ¾ cup granulated sugar, and the 13.4-ounce package instant butterscotch pudding mix on medium-high speed until light and fluffy, about 3–4 minutes.
• Add the 3 large eggs, one at a time, mixing well after each addition. Stir in 1 teaspoon pure vanilla extract.
• With the mixer on low, add half of the flour mixture, then half of the 1 ¼ cups whole milk (or 2%) and mix just until combined. Repeat with the remaining flour mixture and the remaining milk, mixing until batter is smooth and homogenous. Scrape the bowl as needed.
• Divide the batter evenly among the three prepared pans and smooth the tops. Bake for about 30 minutes, or until a toothpick inserted into the centers comes out clean or with a few moist crumbs.
• Let the cakes cool in the pans on a wire rack for 10 minutes. Run a knife around the edges, turn the cakes out onto the rack, remove parchment (if used), and cool completely before frosting.
• While the cakes cool, make the frosting. Melt 1½ cups butterscotch chips until smooth—either in the microwave in 20–30 second intervals, stirring between each, or over a double boiler. Let the melted butterscotch cool slightly so it is warm but not hot.
• In a large mixing bowl, beat 1½ cups unsalted butter (softened) with an electric mixer for about 2 minutes until creamy. Add 6 cups powdered sugar, 1 cup at a time, mixing on low until incorporated and scraping the bowl as needed.
• Add the cooled melted butterscotch and 1 teaspoon pure vanilla extract to the frosting. Add the heavy cream listed in the ingredients (see ingredient list for the amount). Beat on medium-high until the frosting is smooth and fluffy. (If the frosting needs minor thinning or thickening, adjust only with the heavy cream amount provided in the ingredient list.)
• Make the butterscotch ganache: In a small saucepan, heat 3 tablespoons heavy cream just until steaming (do not boil). Remove from heat and pour the hot cream over ½ cup butterscotch chips. Let sit 2 minutes, then stir until completely smooth. Allow the ganache to cool to room temperature before using so it will thicken slightly.
• Level the cooled cake layers with a serrated knife or cake leveler so they stack flat.
• Place one cake layer on a cake plate or turntable. Spread an even layer of frosting over the top. Add the second cake layer, spread another layer of frosting, then place the top layer on.
• Apply a thin layer of frosting to the outside of the stacked cake to create a crumb coat. Smooth lightly, then chill the cake in the refrigerator for at least 30 minutes.
• After chilling, apply a thicker, even layer of frosting to the outside of the cake. Smooth the sides and top as desired. Return the cake to the refrigerator for at least another 30 minutes to set.
• Use a spoon to drizzle the cooled ganache down the sides of the chilled cake to create drips; pour the remaining ganache onto the center of the top and smooth gently to an even layer.
• If desired, pipe additional frosting decorations on top using a piping bag fitted with an open star tip. Store the finished cake refrigerated until serving; bring to room temperature before slicing if preferred.