Preheat oven to 350 F / 175 C. Line four, eight-inch cake pans with parchment paper rounds and spray the sides of the pans with non-stick cooking spray or baking spray. If you don't have 4 cake pans, the batter can sit at room temperature for a few hours. Bake as many layers at a time as you can.

Sift or whisk together 2 ½ cups flour, 2 ½ cups sugar, 1 cup cocoa powder, 2 ½ tsp baking powder, 2 tsp baking soda, and 1 tsp salt in a large bowl. Set aside.

In a separate, large bowl, add 1 ¼ cups warm water, 1 ¼ cups buttermilk, ⅔ cup oil, 3 eggs, and 2 tsp vanilla and whisk together until fully incorporated.

Whisk the dry ingredients into the wet ingredients until they're just combined, and the batter is smooth.

Divide the batter evenly between the prepared cake pans and bake for 22-25 minutes or until a toothpick comes out with a few moist crumbs.

Let the pans cool for 10 minutes, then run a small offset spatula around the perimeter of the pan to separate the cake from the pan.

Place the cake pans into the freezer for 30 minutes to accelerate the cooling process. This helps lock in the steam and makes the layers extra moist. If you don't have room in the freezer, place the cake pans on a wire rack and let them cool fully before removing them.

Once the layers are fully cooled, carefully flip the pans, and remove the layers.

These cake layers bake up pretty flat so leveling them is optional, but I like to level them with a serrated to make the cake easier to fill and frost.

If you make these cake layers in advance and freeze them, let them thaw for about 15 minutes before making the cake. The cake layers should still be slightly cold to the touch, which will make it easier to assemble the cake.

Make the caramel while the cake layers bake and cool. This can be made up to 2 weeks in advance.

Place a medium saucepan over medium to medium-high heat. Once the pan has warmed up, pour in 2 cups of sugar gradually, adding ¼ cup at a time. Stir as needed with a rubber spatula. Wait until the sugar is mostly dissolved, then add in the next bit of sugar. As the sugar melts it will gradually deepen in color.

Stir occasionally until the sugar is fully dissolved and has become an amber color, then turn off the heat.

Slowly mix in ¾ cup of butter (2 Tbsp at a time), then stir in ½ cup of heavy cream and ½ tsp salt. Note: sometimes the butter has a hard time incorporating into the sugar if it's been cooked a bit too long or at too high of a heat! If this happens to you, you may want to turn the heat down a bit the next time you make it or use a heavier-bottomed pan that can help the sugar cook more evenly. But don't worry! You can gradually stir the butter into the caramel as it cools, and it should incorporate back together. The mixture will be thin but will thicken as it cools. Pour into a separate container, then place in the fridge to speed up the cooling process.

Once the caramel has reached room temperature, whip it with a hand mixer or stand mixer on a medium-high speed for 1-2 minutes, until it becomes lighter in color and looks thicker. Place ⅓ cup of caramel into a small piping bag, seal the top with a rubber band, and set aside. Then fold in ¾ cup of salted, chopped peanuts into the remaining caramel. Set aside.

While the cake layers and caramel cool, make the buttercream frosting. In a large bowl or the bowl of a stand mixer, beat 1 ½ cups of butter and 1 cup of creamy peanut butter on a medium-high speed for 1 minute with a paddle attachment or hand mixer until smooth and fluffy.

Mix in 1 tsp vanilla extract and ½ tsp salt on a low speed until the ingredients are incorporated.

Gradually mix in 7 cups of powdered sugar and ⅔ cup of heavy cream on a low speed. Scrape the sides and bottom of the bowl as needed with a rubber spatula.

Mix on low until the desired consistency is reached. If the frosting seems too thick, add in additional cream (1 Tbsp at a time). If the frosting seems too thin, add in more powdered sugar (¼ cup at a time).

Place a third of the frosting into a large piping bag fitted with a large round piping tip or cut an opening about ¾-inch at the base of the bag. Cover the remaining frosting with plastic wrap to prevent crusting and set aside.

Then it's time to assemble the cake. Stack and frost the cake layers on a greaseproof cake board or flat plate using a dab of buttercream to help stick the first cake layer to the board.

Spread an even layer of buttercream on top of the cake layer. Then pipe a buttercream ring around the cake layer's edge and fill the center with a third of the peanut caramel.

Repeat with the remaining cake layers. Flip the top cake layer upside down to make the cake easier to frost and minimize crumbing.

Once the layers are stacked, chill the cake in the freezer for 10 minutes or in the fridge for 20 minutes to prevent the layers from sliding. Then use the remaining frosting to cover the cake. Smooth the frosting using a bench scraper or large offset spatula.

Gently press chopped peanuts around the base of the cake. Then chill the cake in the fridge (20 minutes) or freezer (5 minutes) until the frosting is firm to the touch.

While the cake chills, make the chocolate ganache.

Heat ⅓ cup of heavy cream in a heatproof bowl in the microwave for 30-45 seconds, until it's just beginning to bubble. Gently pour ½ cup of milk chocolate chips into the heavy cream, making sure they are fully covered with cream. If you want to use dark chocolate, use ⅔ cup of heavy cream and ½ cup dark chocolate.

Let the mixture sit for 1 minute, then stir until the cream and chocolate are combined and smooth. If the mixture seems too thin or thick, you can add a touch more chocolate chips or heavy cream. The type of cream and chocolate that you use can affect the consistency, along with the temperature of the ganache. Feel free to adjust as needed.

Drizzle the remaining caramel that was placed in a piping bag over the edge of the chilled cake. If the caramel has cooled off too much and is challenging to squeeze out of the bag, heat it in the microwave in 5-second intervals until it's at room temperature again. It will seem really thick and the drips may seem short, but they should lengthen / thin out after a few minutes (see how thick mine were at the start of the video!)

Then pour the chocolate ganache on top of the cake and gently push it over the edge of the cake using a small offset spatula.

Add a ring of chopped-up Snickers around the top of the cake, then top with a sprinkle of sea salt and enjoy!