Creating the Sweet & Salty Millionaire's Layer Cake is straightforward if you follow these simple steps:

1. Prepare the Oven: Preheat your oven to 350°F (175°C) and grease and flour three 9-inch round cake pans.
2. Mix Dry Ingredients: In a large bowl, combine the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Whisk together until well blended.
3. Combine Wet Ingredients: In another bowl, beat the eggs and then mix in the milk, vegetable oil, and vanilla extract.
4. Incorporate Boiling Water: Slowly add the boiling water to the wet ingredients, mixing until smooth. The batter will be thin.
5. Combine Mixtures: Gradually add the dry ingredients to the wet mixture, stirring until fully combined.
6. Bake Cakes: Divide the batter equally among the prepared pans. Bake in the preheated oven for 30-35 minutes or until a toothpick inserted in the center comes out clean.
7. Cool Cakes: Once baked, remove from the oven and let the cakes cool in the pans for 10 minutes before transferring them to wire racks to cool completely.
8. Make Salted Caramel: In a medium saucepan over medium heat, melt the granulated sugar until it becomes amber in color, stirring constantly. Remove from heat and whisk in the butter. Slowly add the heavy cream, stirring until smooth. Mix in the sea salt and let cool slightly.
9. Assemble the Cake: Once the cakes are cool, layer them on a serving plate. Spread a layer of caramel sauce between each cake layer and on top of the final layer.
10. Garnish: Optionally, top with whipped cream and sprinkle with sea salt flakes.