Classic Vanilla Cake with Butterscotch Filling and Buttercream

Vanilla cake filled with a creamy butterscotch center and finished with vanilla buttercream is our family’s favorite birthday cake. Use this recipe to make it for your next celebration.

Every year my sons ask for this cake, so I consider it the best vanilla cake recipe. The cake stays moist, the butterscotch filling is rich without being overly sweet, and the vanilla buttercream ties everything together for a classic, crowd-pleasing dessert.

Vanilla Cake with Butterscotch Filling and Vanilla Buttercream Icing

Ingredients

For the vanilla cake:

• 2 ½ cups all-purpose flour
• 2 cups granulated sugar
• 1 teaspoon baking powder
• ½ teaspoon baking soda
• 1 1/3 cups buttermilk or sour milk (to make sour milk: add 1 tablespoon vinegar or lemon juice to a 2-cup measuring cup, then add milk until you reach 1 1/3 cups)
• ½ cup shortening, margarine, or butter
• 1 teaspoon vanilla extract
• 4 egg whites

For the butterscotch filling:

• 1 cup packed brown sugar
• 3 tablespoons all-purpose flour
• 1 cup milk
• 2 egg yolks, lightly beaten
• 2 tablespoons butter
• 1 teaspoon vanilla extract

For the vanilla buttercream icing:

• 1/3 cup butter or margarine, softened
• 4 ½ cups sifted powdered sugar
• ¼ cup milk
• 1 ½ teaspoons vanilla extract
• Additional milk as needed for spreading consistency

Step 1 — Bake the vanilla cake and cool completely

Preheat the oven to 350°F (175°C). Grease and line two 9×1½ inch round baking pans with parchment paper.

1. In the bowl of a stand mixer or a large bowl, combine the flour, sugar, baking powder, baking soda, and 1/8 teaspoon salt. Mix briefly on low speed to combine.
2. Add the buttermilk (or sour milk), shortening (or butter/margarine), and vanilla. Beat on low for 30 seconds, scraping the bowl, then increase to medium-high and beat for 2 minutes, scraping the sides again as needed.
3. Add the egg whites and beat for another 2 minutes, until the batter is smooth and well combined.
4. Divide the batter between the prepared pans and smooth the tops. Bake for 30–35 minutes, or until a toothpick inserted near the center comes out clean.
5. For even baking, place the pans on two oven racks staggered; halfway through baking swap the pan positions. When done, cool the cakes on wire racks for 10 minutes, loosen the sides, remove from pans, and cool completely before filling and frosting.

Tip: Use parchment rather than wax paper for lining pans. Cooling the layers fully before assembling ensures the filling and frosting set properly.

Step 2 — Make the butterscotch filling and assemble

The butterscotch filling is a simple, custard-style center that spreads easily and adds rich flavor.

1. In a medium saucepan, combine the brown sugar and flour. Gradually stir in the milk until smooth.
2. Cook over medium heat, stirring constantly, until the mixture thickens and comes to a gentle boil. Continue to boil for 1 minute while stirring.
3. Remove from heat. Slowly whisk at least half of the hot mixture into the beaten egg yolks to temper them, then return the egg mixture to the saucepan and stir to combine.
4. Return to a gentle boil for 1 minute while stirring constantly. Remove from heat and stir in the butter and vanilla. Allow the filling to cool completely to room temperature before using.
5. Place one cooled cake layer on a serving plate. Spread the cooled butterscotch filling over the top, leaving about a 1-inch border to prevent the filling from spilling over when the top layer is added. Top with the second cake layer.

Step 3 — Make the vanilla buttercream and frost the cake

1. In a mixing bowl, beat the softened butter until light and fluffy.
2. Gradually add 2 cups of the powdered sugar, beating well. Slowly add the ¼ cup milk and the vanilla extract, mixing until smooth.
3. Beat in the remaining powdered sugar. If the frosting is too stiff, add additional milk a teaspoon at a time until it reaches a spreadable consistency. Use the buttercream to frost the top and sides of the assembled cake. This amount should cover two 8–9 inch layers.

Notes and tips

• Room temperature ingredients (egg whites, milk, butter) blend more evenly and give a smoother batter.
• To avoid a runny filling, ensure the butterscotch custard is fully cooled before assembling the cake.
• If you prefer a firmer filling border, pipe a thin ring of buttercream on the edge of the bottom layer before adding the butterscotch; this creates a dam that helps contain the filling.
• Leftover cake keeps well covered at room temperature for one day or refrigerated for several days. If refrigerated, bring to room temperature before serving for best flavor and texture.

Nutrition (approximate per serving)

Yield: 12 servings. Amounts below are estimates provided for reference only.

• Calories: 707
• Total fat: 22g (saturated fat: 10g, trans fat: 1g)
• Cholesterol: 69mg
• Sodium: 288mg
• Carbohydrates: 122g (fiber: 1g, sugar: 95g)
• Protein: 8g

Enjoy this classic combination of moist vanilla cake, smooth butterscotch filling, and creamy vanilla buttercream. It’s a simple yet special cake that’s ideal for birthdays and family gatherings.