Preheat Oven and Prepare Ingredients
Preheat oven to 350°F (175°C)
Grease baking pan or cake tins
Sift flour, baking soda, cornstarch, salt
Mixing Wet Ingredients
Combine butter, vegetable oil, sugar, and peanut butter
Beat with an electric mixer on medium speed for 3 minutes
Add eggs one at a time, mixing well
Mix in vanilla extract and buttermilk
Combining Dry and Wet Ingredients
Gradually add dry ingredients to the wet mixture
Fold with a spatula to avoid overmixing
Result: smooth, creamy batter
Baking the Cake
Pour batter into prepared pan, distribute evenly
Bake for 30 minutes or until the toothpick comes out clean
Cool in pan for 5 minutes, then transfer to wire rack
Making the Frosting
Melt butter and peanut butter together in a saucepan
Stir in milk, powdered sugar, and a pinch of salt
Mix until smooth and creamy
Assembling the Cake
Spread frosting evenly over cooled cake
Optionally, add ganache or drizzle with chocolate
Storing the Cake
Store in a freezer-safe container for up to 3 days
Alternatively, wrap tightly and refrigerate for freshness