Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

Mix Dry Ingredients: In a large mixing bowl, combine the flour, 1 1/2 cups sugar, cocoa powder, baking powder, baking soda, and salt. Mix well.

Add Wet Ingredients: Add the buttermilk, vegetable oil, eggs, and 2 teaspoons vanilla extract to the dry ingredients. Beat on medium speed for 2 minutes until well combined.

Add Boiling Water: Stir in the boiling water until the batter is smooth. The batter will be thin.

Bake Cakes: Pour the batter evenly into the prepared pans. Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.

Cool: Allow the cakes to cool in the pans for 10 minutes before transferring to wire racks to cool completely.

Make Caramel: In a medium saucepan over medium heat, melt the 1 cup sugar, stirring constantly until it turns a golden brown color.

Finish Caramel: Add the 6 tablespoons butter and stir until melted. Carefully pour in the heavy cream and 1 teaspoon vanilla extract, stirring until smooth. Remove from heat and let cool slightly.

Make Crunch Topping: In a bowl, combine the crushed graham crackers, chopped pecans, coconut flakes, and 1/4 cup melted butter. Mix until well combined.

Assemble Cake: Once the cakes are cool, place one layer on a serving plate. Drizzle with half of the caramel sauce and sprinkle with half of the crunch topping.

Finish Assembly: Place the second cake layer on top and repeat with the remaining caramel sauce and crunch topping.

Serve: Serve immediately or refrigerate leftovers.