Preheat your oven to 160°C (320°F) and prepare two 8-inch round cake tins by greasing them with butter or lining with parchment paper.

In a large mixing bowl, sift together the all-purpose flour, cornstarch, baking powder, and salt, then set aside.

In a separate bowl, use an electric mixer to cream the unsalted butter, granulated sugar, and brown sugar until fluffy and light, about 3 to 5 minutes.

Add the eggs one at a time, mixing well after each addition, followed by the sour cream and vanilla extract.

Gradually add the dry ingredients to the wet mixture, alternating with the full-fat milk, mixing until just combined.

Pour the batter evenly into the prepared cake tins and bake for 28–30 minutes or until a toothpick inserted comes out clean.

In a saucepan, combine the unsalted butter, granulated sugar, evaporated milk, and salt. Stir over medium heat until thickened.

Once removed from heat, stir in the heavy cream and vanilla extract for the frosting.

After cooling, level the cake layers and frost generously with the caramel frosting, stacking layers as desired.