Preheat the Oven:

Preheat your oven to 350°F. Grease and line two 9-inch round cake pans with parchment paper.

Make the Cake Batter:

In a large bowl, whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt. Add eggs, milk, vegetable oil, and vanilla. Beat on medium speed for 2 minutes. Stir in boiling water (the batter will be thin).

Bake the Cake:

Divide the batter evenly between the prepared pans and bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean. Cool in the pans for 10 minutes, then remove from pans and cool completely on wire racks.

Prepare the Salted Caramel:

In a saucepan over medium heat, melt the sugar, stirring constantly until it turns amber in color. Add the butter and stir until melted. Gradually add the cream, stirring constantly, until smooth. Stir in sea salt and let it cool slightly.

Make the Chocolate Frosting:

In a large bowl, beat the softened butter until creamy. Add cocoa powder and powdered sugar alternately with heavy cream, beating until smooth. Stir in vanilla extract.

Assemble the Cake:

Spread a layer of chocolate frosting over the first cake layer. Drizzle with salted caramel. Add the second cake layer and frost the entire cake. Drizzle more caramel on top and sprinkle with sea salt.

Serve:

Slice and enjoy this decadent salted caramel chocolate cake!