Preheat the oven to 350°F (176°C) and prepare three 8-inch cake pans by spraying them with non-stick baking spray and lining the bottoms with parchment paper.

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

In a medium bowl, whisk together the milk, vegetable oil, vanilla extract, and eggs.

Add the wet ingredients to the dry ingredients and mix until well combined.

Gradually pour in the hot water, mixing on low speed until smooth. Scrape the sides of the bowl as necessary to ensure everything is thoroughly combined.

Evenly divide the batter among the prepared cake pans and bake for 22-25 minutes, or until a toothpick inserted comes out with just a few moist crumbs.

Allow the cakes to cool in the pans for 2-3 minutes before transferring them to a cooling rack to finish cooling.

In a large mixing bowl, beat together the butter and peanut butter until smooth.

Add half of the powdered sugar and mix until smooth.

Add 3 tablespoons of water or milk and mix until fully incorporated.

Add the remaining powdered sugar and mix until smooth again.

Add the remaining water or milk and mix until smooth, checking the consistency to avoid making the frosting too thin.

Use a large serrated knife to level the tops of the cake layers so they are flat. (For tips on leveling and stacking cakes, refer to my instructions.)

Place the first cake layer on a serving plate or cake board, then spread about 1 cup of frosting on top. Smooth the frosting into an even layer.

Sprinkle half of the chopped Reese’s on top of the frosting and gently press them into the frosting. Spread a small amount of frosting on top of the Reese’s to create a sticky surface for the next cake layer.

Add the second cake layer and repeat the frosting and Reese’s process, spreading about 1 cup of frosting on top and pressing the remaining chopped Reese’s into it.

Place the final cake layer on top.

Smooth frosting over the sides of the cake, creating a thin crumb coat.

Spread about 1 cup of frosting on top of the cake and smooth it into an even layer.

Frost the cake as shown in my tutorial for a smooth finish, stopping just before using a paper towel, as the pattern on the sides of the cake will make it unnecessary.

Use an offset spatula to create stripes around the sides of the cake (for a step-by-step guide, watch the video starting at 1:40).

Set aside the cake and begin preparing the chocolate ganache.

Place the chocolate chips in a heatproof bowl.

Microwave the heavy whipping cream until it just begins to boil, then pour it over the chocolate chips. Let it sit for 2-3 minutes before whisking until smooth.

Using a spoon or squeeze bottle, drizzle the ganache around the edges of the cake, then fill the top and smooth it out with an offset spatula. (For more tips on creating a chocolate drip cake, refer to my instructions.)

Allow the ganache to firm up for about 10 minutes before topping the cake with swirls of the remaining frosting. Use a piping bag fitted with a closed star tip—Ateco tip 844, Wilton 2D, or Wilton 1M will all work well.

Top with additional Reese’s, halved, and sprinkle with crumbled Reese’s for decoration.

Refrigerate the cake until ready to serve. Be sure to serve it at room temperature for the best texture and flavor. The cake is best consumed within 3-4 days.