Preheat your oven to 350°F (175°C). Grease and flour the two 9-inch round cake pans and line the bottoms with parchment paper.

In a large mixing bowl, combine the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Mix well.

Add the eggs, milk, vegetable oil, and vanilla extract to the dry ingredients. Using an electric mixer, beat the mixture on medium speed for about 2 minutes.

Carefully stir in the boiling water until the batter is well combined (the batter will be thin).

Pour the batter evenly into the prepared cake pans. Bake in the preheated oven for 30 minutes, or until a toothpick inserted in the center comes out clean.

Once baked, remove the cakes from the oven and let them cool in the pans for about 10 minutes before transferring them to a cooling rack to cool completely.

For the caramel layer, heat the caramel sauce and heavy cream in a saucepan over low heat, stirring until smooth. Set aside.

Once the cakes are cooled, place one layer on a serving plate. Drizzle half of the caramel mixture over the cake layer.

Add the second cake layer on top, pouring the remaining caramel sauce over it.

For the toffee crunch, sprinkle the toffee bits evenly over the top of the cake, followed by the chocolate chips.

Allow the cake to sit for at least 15 minutes to set before slicing and serving.