1. Preheat oven to 325 degrees. Prepare three 9 inch cake pans with parchment rounds in the bottom of the pans and grease the sides.
2. With the whisk attachment of your mixer, beat the butter for 2 minutes on high speed.
3. Add the sugar then beat for another 5 minutes with the beater attachment until pale yellow and fluffy.
4. Add the eggs one at a time, combining well after each addition and scraping down the sides of the bowl as needed.
5. With your mixer on low speed, add the flour in two batched.
6. Add the salt, baking powder and baking soda and mix until well combined, careful not to overbeat.
7. Add the sour cream, oil and vanilla extract. Scrape down the sides and bottom of the bowl and mix until just combined. The batter should be nice and silky.
8. Divide the batter between the three pans and bake for 27-32 minutes or until a toothpick inserted into the center comes out with a few crumbs.
9. Let the layers cool for about 10 minutes, then finish cooling on wire racks.
Phase 1, takes about 20-30 minutes
In a medium saucepan over medium-low heat, melt the evaporated milk, sugar, butter and salt. Continue cooking. The butter will begin to separate and create and yellow, oily film.
Phase 2, takes about 60 minutes
The bulk of the process is this phase. The ingredients will come to a slow boil and form bubbles on the surface. As you continue cooking, the bubbles will get bigger and become more numerous. Stir occasionally as it all comes together.
Phase 3, takes about 15 minutes
Some white clumps will develop on the surface. This is normal. Just continue to cook and stir occasionally to blend everything back together. You should start to see the mixture turn a light golden caramel color. The color will slowly deepen and the car male will bubble higher.
Phase 4, takes about 10-15 minutes
Reduce the heat to low to ensure you don’t burn the caramel. The bubbling will subside into a simmer as everything thickens. The caramel should be an amber brown when done and coat the back of a spoon. Once that happens, remove from heat and add in vanilla extract. Allow the caramel to cool for about 30 minutes and thicken before layering the cake.
To finish the cake
1. Place first layer on serving plate. Spread about 1/3 of the caramel on top of the cake. The icing may drip down the sides a bit, but that’s ok.
2. Add the second layer of cake and another 1/3 of the icing.
3. Add the final layer, bottom up, and ice the top and sides of the cake with a thin layer of caramel.
4. Pour remaining caramel over the cake and allow to drizzle down the sides.