Preheat your oven to 350°F (180°C). Grease and flour two 9-inch round cake pans, ensuring the batter will slide out easily once baked.

In a large mixing bowl, combine the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Whisk until the mixture is even.

In another bowl, whisk together the eggs, milk, vegetable oil, and vanilla extract until fully combined.

Gradually mix the wet ingredients into the dry mixture, stirring until you have a smooth batter. Lastly, pour in the boiling water and mix until well incorporated.

Split the batter evenly between the prepared pans. Bake in the preheated oven for about 25 minutes, or until a toothpick inserted in the center comes out clean.

While your cakes are baking, make the salted caramel. In a medium saucepan over medium heat, cook the sugar, stirring occasionally until it melts and turns a golden color. Be cautious not to burn it!

Once the sugar is melted, quickly add the butter and stir until combined. Slowly pour in the heavy cream, continuing to stir. Finally, remove from heat and mix in the sea salt. Let it cool slightly.

Once the cakes have cooled, place one layer on a serving plate. Pour a generous amount of salted caramel over the top, then add the second layer. Drizzle more salted caramel on top and sprinkle a little sea salt for that extra indulgent touch.

Slice and serve your cake at room temperature, or chill it in the fridge for a firmer texture.