1. Preheat your oven to 350°F (175°C). Prepare two 9-inch round cake pans by greasing them with butter and dusting with flour, or lining them with parchment paper for easy removal.

2. In a large mixing bowl, add the flour, granulated sugar, cocoa powder, baking powder, baking soda, and salt. Sift these dry ingredients together to ensure there are no lumps and everything is well combined.

3. Next, add the eggs, milk, vegetable oil, and vanilla extract to the bowl of dry ingredients. Beat the mixture with an electric mixer on medium speed for about 2 minutes, until the batter is smooth and fully combined.

4. Carefully stir in the boiling water or hot coffee. The batter will be quite thin, but this will help create moist, tender cake layers.

5. Divide the batter evenly between the two prepared cake pans. Bake in your preheated oven for 30-35 minutes, checking for doneness with a toothpick inserted into the center—it should come out clean.

6. Once baked, let the cakes cool in their pans for around 10 minutes. Then, gently turn them out onto wire racks to cool completely before frosting.

7. While the cakes cool, prepare the caramel frosting. In a medium saucepan, melt the unsalted butter over medium heat. Stir in the brown sugar and cook while constantly stirring for about 2 minutes. Gradually add in the milk, bring it to a gentle boil, then remove from heat. Allow to cool slightly.

8. Whisk the powdered sugar into the butter mixture until the frosting is smooth and creamy. Finally, stir in the vanilla extract.

9. To assemble the cake, place one of the baked layers on your serving plate. Spread a generous layer of caramel sauce on top and sprinkle half of the crushed Butterfinger candy bars over the sauce.

10. Gently place the second layer of the cake on top and frost the entire cake with the caramel frosting. Top it off with the remaining crushed Butterfinger pieces.

11. If you like, drizzle extra caramel sauce on top for an even sweeter finish. Cut into slices, serve, and revel in every rich, gooey bite of this phenomenal dessert!

Nutritional Information: This cake is rich, offering a balance of sweetness and decadence with a combination of carbohydrates, fats, and protein. Each slice contains approximately 450 calories with key nutrients from the chocolate, butter, and the Butterfinger pieces.