01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together all-purpose flour, baking powder, baking soda, and fine sea salt until evenly combined.
03 - In a large bowl, beat softened butter, vegetable oil, light brown sugar, and granulated sugar on medium speed until pale and fluffy, approximately 3 minutes.
04 - Add eggs one by one, beating thoroughly after each. Mix in vanilla extract and butter flavoring.
05 - Alternate adding the dry ingredient mixture in three parts with buttermilk and cream soda, starting and ending with dry ingredients. Mix just until incorporated; avoid overmixing.
06 - Pour batter evenly into prepared cake pans and smooth the surface. Bake for 24 to 28 minutes, or until a toothpick inserted in the center emerges clean.
07 - Allow cakes to rest in the pans for 10 minutes. Unmold onto wire racks and cool completely before assembly.
08 - Beat softened butter and light brown sugar together until smooth and fluffy. Gradually incorporate confectioners’ sugar. Add heavy cream, vanilla extract, butter flavoring, and salt. Continue beating until light and spreadable; add extra cream as necessary for consistency.
09 - Melt unsalted butter in a small saucepan over medium heat. Stir in light brown sugar and cook for 2 minutes, stirring constantly. Slowly add heavy cream and salt. Simmer for 3 to 4 minutes, stirring often, until thickened. Remove from heat and blend in vanilla extract. Let sauce cool to room temperature.
10 - Level the cooled cake layers as needed. Place one layer on a serving plate and generously spread with frosting. Repeat with the remaining layers.
11 - Apply remaining frosting to the top and sides of the cake, creating swirls for a rustic, messy appearance.
12 - Pour butterscotch sauce generously over the cake, allowing it to run down the sides.
13 - Adorn cake with gold sprinkles and crushed butterscotch candies if desired. Serve immediately or store at room temperature.