Prepare the Chocolate Cake:

1. Preheat the Oven: Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.
2. Mix Dry Ingredients: In a large mixing bowl, combine the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt.
3. Add Wet Ingredients: Add the eggs, milk, vegetable oil, and vanilla extract to the dry ingredients. Mix on medium speed using an electric mixer until smooth and well combined.
4. Add Boiling Water: Slowly add the boiling water to the batter, mixing gently. The batter will be thin, but that’s perfectly fine—it will make for a moist cake.
5. Bake the Cake: Pour the batter evenly into the prepared pans. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for 10 minutes, then remove them from the pans and place on a wire rack to cool completely.

Make the Caramel Layer:

6. Prepare the Caramel: In a medium saucepan, melt the butter over medium heat. Stir in the brown sugar and cook for 2-3 minutes until the sugar is dissolved.
7. Add Cream and Vanilla: Pour in the heavy cream and bring to a simmer, stirring constantly. Allow the caramel to bubble for about 2 minutes, then remove from heat and stir in the vanilla extract. Let it cool for 10-15 minutes.
8. Add Pecans: Stir in the chopped pecans and set the caramel mixture aside.

Make the Chocolate Ganache:

9. Prepare the Ganache: In a heatproof bowl, place the chopped semisweet chocolate. Heat the heavy cream and butter in a saucepan over medium heat until it just begins to simmer.
10. Mix Ganache: Pour the hot cream mixture over the chopped chocolate and let it sit for a minute. Stir until the chocolate is completely melted and the ganache is smooth.

Assemble the Cake:

11. Layer the Cake: Place the first cake layer on a serving platter. Spread a generous amount of the caramel mixture over the top of the first layer, making sure it’s evenly covered.
12. Add the Second Cake Layer: Place the second cake layer on top of the caramel layer.
13. Top with Ganache: Pour the chocolate ganache over the top of the cake, allowing it to drip down the sides for a decadent look.
14. Garnish the Cake: Sprinkle the top of the cake with the remaining chopped pecans, and if desired, lightly sprinkle with sea salt for an extra touch.

Chill and Serve:

15. Chill the Cake: Allow the cake to chill in the refrigerator for 30 minutes to set the ganache before serving. This helps the flavors meld together.
16. Serve: Slice and enjoy this indulgent dessert! The cake can be served with a scoop of vanilla ice cream or a dollop of whipped cream, if desired.