• Preheat the oven to 350º F. Grease two or three 8 inch springform pans with butter (butter the sides and bottom) and line each pan with a parchment paper circle for easy cake removal. Set aside.
• In a small mixing bowl combine the flour, baking powder, baking soda, and salt.
  2 ½ cups (300g) all-purpose flour, 2 tsp baking powder, ½ tsp baking soda, 1 tsp salt
• In a large mixing bowl combine the butter, sugar, and vegetable oil, beat using an electric mixer, 1-2 minutes until fluffy.
  ¾ cup (170g) unsalted butter, 1 ¾ cups (346g) granulated sugar, ¼ cup (59ml) vegetable oil
• Add in the eggs, sour cream, milk, and vanilla extract. Beat with the electric mixer.
  4 large eggs, 1 cup (227g) sour cream, ½ cup (118ml) milk, 1 Tbsp vanilla extract
• Gradually add the flour mixture to the wet ingredients, mixing just until the flour is incorporated.
• Evenly divide the batter among the pans. If using 2 pans, that’s 3 cups of batter per pan, if using 3 pans, that’s 2 cups of batter per pan. If you have bake even cake strips, soak them, then secure them around the outside of the pans.
• Bake 2 pans for 40-50 minutes or 3 pans for 32-37 minutes or until a toothpick inserted in the center comes out clean.
• Allow the cakes to cool for 20-30 minutes in the pans, then use a small spatula to loosen the cake from the edge of the pan. Remove the cake from the pans and allow them to cool completely on a cooling rack.

Frosting

• In a mixing bowl, combine the butter, vanilla extract and salt, beat using an electric mixer until fluffy, 1-2 minutes.
  2 ½ cups (565g) unsalted butter, 2 Tbsp vanilla extract, ⅛ tsp salt
• Gradually add the powdered sugar and 3 tbsp of heavy cream, mixing on low until combined.
  6-10 cups (681-1135g) powdered sugar, 3-6 Tbsp milk or heavy cream if frosting becomes too thick
• Taste as needed to determine if you want more powdered sugar. If the frosting becomes too thick, add 2-4 tablespoons of milk or heavy cream.

Assemble the Cake

• If needed, level the cooled cakes using a cake levered or serrated knife.
• Spread a small amount of frosting on the bottom of your cake plate / stand, this acts as “glue” to prevent the cake from moving. Place one cake layer over the frosting. Measure 3/4 to 1 cup of frosting and evenly spread that on top of the first layer. Top with the second cake layer and spread another ¾ to 1 cup of frosting on top of that layer. Use the remaining frosting around the sides and top of the cake.