Prepare Chocolate Cake:

• Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
• In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.
• In a separate bowl, combine buttermilk, oil, eggs, and vanilla extract.
• Gradually add wet ingredients to dry ingredients, mixing until just combined.
• Stir in hot coffee. Pour batter evenly into prepared pans.
• Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
• Let cakes cool in pans for 10 minutes, then invert onto a wire rack to cool completely.

Make Caramel Filling:

• In a medium saucepan, combine sugar and water over medium heat. Cook without stirring, until sugar dissolves and turns amber.
• Carefully whisk in heavy cream, butter, and salt. Cook until smooth and slightly thickened.
• Let cool slightly.

Prepare Toffee Crunch:

• Line a baking sheet with parchment paper.
• In a saucepan, combine butter, sugar, and water. Cook over medium heat until golden amber.
• Remove from heat and stir in baking soda and toffee bits.
• Pour onto prepared baking sheet and let cool completely. Break into small pieces.

Make Frosting:

• In a large bowl, beat butter until creamy.
• Gradually add powdered sugar and cocoa powder, mixing on low speed until combined.
• Beat in heavy cream, vanilla extract, and salt until smooth and creamy.

Assemble Cake:

• Level the tops of the cooled cakes.
• Place one cake layer on a serving plate. Spread half of the caramel filling over the cake.
• Sprinkle half of the toffee crunch over the caramel.
• Top with the second cake layer.
• Frost the entire cake with the chocolate frosting.
• Drizzle remaining caramel filling over the top and sprinkle with the remaining toffee crunch.

Serve: Slice and serve.