Preheat your oven to 160°C (320°F) with the fan on. If your oven doesn’t have a fan function, refer to Note 1 for adjustment. Grease or line two 8-inch cake tins. (I personally use my homemade cake release for best results.)

In a medium bowl, sift together the flour, cornstarch, baking powder, and salt. Use a whisk or fork to mix thoroughly until well combined. Set this dry mixture aside.

In a large mixing bowl, combine the butter, vegetable oil, white granulated sugar, and brown sugar. Using an electric mixer—either hand-held or stand mixer (see Note 2)—cream the mixture on medium speed for about 2 minutes until light and fluffy.

Add the eggs one at a time, mixing well between each addition (about 10–15 seconds per egg) to fully incorporate.

Next, add the sour cream and vanilla extract. Mix until everything is well combined. Set the mixer aside at this point—the rest of the batter will be mixed gently by hand.

Add half of the dry ingredients to the wet mixture. Using a spatula, fold gently until just combined—do not overmix. Then add the milk and fold again just until combined. Finally, add the remaining dry ingredients and fold until just incorporated. Be careful not to overmix the batter (see Note 3).

Evenly distribute the batter between the two prepared cake tins. Bake for 28–30 minutes, or until a toothpick inserted in the center comes out clean.

Once baked, let the cakes cool in their tins for 15–20 minutes. Then carefully turn them out onto a wire rack to cool completely before applying the caramel frosting.

Place a large saucepan over medium heat and add the butter, granulated sugar, evaporated milk, and salt. Stir continuously as everything melts together and comes to a simmer. Once it begins simmering, reduce the heat to low or low-medium.

Let the caramel cook and thicken slowly for about an hour, stirring every few minutes to prevent burning. As the mixture thickens—especially toward the end of the cooking time—keep a closer eye on it, as it's more prone to scorching at this stage. When the caramel becomes thick, smooth, and deep golden brown (refer to the video for visual cues), stir in the cream and vanilla extract. Mix well until fully combined.

Immediately pour the hot caramel into a heatproof bowl and allow it to cool for about 25 minutes. The caramel should still be warm and pourable when you start frosting, as it will firm up quickly once applied. (See Note 4 if the caramel thickens too much.)

Once the cake layers are completely cool, level the tops with a serrated knife to ensure flat, even layers.

Place the first cake layer on your cake stand or serving platter. Spread a generous amount of the warm caramel frosting over the top and smooth it out using an offset spatula or knife.

Place the second cake layer on top. Cover the top and sides of the cake with more caramel frosting. If the caramel seems too thin or isn’t setting properly, refer to Note 5 for troubleshooting.

As the caramel begins to set, it will develop a shiny finish. For a polished look, gently run your offset spatula or knife over the shiny surface to smooth it out further. Decorate however you like—and enjoy!