Preheat your oven to 160 °C (320°F) and prepare two 8-inch cake pans with butter or parchment paper.

Sift together the flour, cornstarch, baking powder, and salt in a mixing bowl.

In a mixing bowl, cream together the unsalted butter, vegetable oil, white sugar, and brown sugar for about 2 minutes until light and creamy.

Add the eggs one at a time, blending well after each addition.

Stir in the sour cream and vanilla extract until fully combined.

Fold in half of the dry ingredients, then pour in the milk and gently fold until just combined.

Add the remaining dry ingredients, folding until no flour streaks remain, being careful not to over-mix.

Distribute the batter evenly between the two prepared cake pans.

Place the pans in the preheated oven and bake for 28-30 minutes, or until a toothpick inserted comes out clean.

Allow the cakes to cool in the pans for 15-20 minutes before transferring to a wire rack to cool completely.

In a saucepan over medium heat, combine the butter, sugar, evaporated milk, and salt. Stir frequently and allow to simmer.

Let it simmer while constantly stirring until thickened, around 1 hour.

Stir in the cream and vanilla extract, then remove from heat and let cool slightly.

Level the cooled cake layers if necessary for even frosting.

Place one layer on a serving plate, spread caramel frosting, and then place the second layer on top. Frost the top and sides of the cake.

Decorate with extra caramel drizzle or chopped nuts if desired. Serve and enjoy!