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

In a large mixer bowl, combine flour, sugar, cocoa powder, baking soda, baking powder, and salt.

In a medium bowl, combine milk, vegetable oil, vanilla extract, and eggs.

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

Slowly add hot water to the batter and mix on low speed until well combined. Scrape down the sides of the bowl as needed.

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.

Remove cakes from oven and allow to cool for 2-3 minutes, then transfer to a cooling rack to finish cooling.

In a large mixer bowl, combine butter and peanut butter and mix until well combined.

Add half of the powdered sugar and mix until smooth. Add 3 tablespoons of water or milk and mix until smooth.

Add remaining powdered sugar and mix until smooth. Add remaining water or milk, and salt, and mix until smooth, checking frosting consistency.

Use a large serrated knife to level the tops of the cooled cake layers.

Place the first cake layer on a serving plate or cardboard cake circle and top with about 1 cup of frosting. Smooth into an even layer.

Sprinkle half of the chopped Reese's on top of the frosting and press down slightly. Spread a small amount of frosting on top of the Reese's to make it sticky.

Add the second cake layer and top with about 1 cup of frosting, smoothing it out. Add the remaining chopped Reese's on top of the frosting and press them in. Spread a small amount of frosting on top to make it sticky for the final layer.

Place the final cake layer on top. Apply a thin crumb coat of frosting around the sides of the cake and top with an additional cup of frosting, smoothing into an even layer.

Use an offset spatula to create stripes around the cake.

To make the ganache, place chocolate chips in a heatproof bowl. Microwave heavy whipping cream until just beginning to boil, then pour over the chocolate chips. Let sit for 2-3 minutes and whisk until smooth.

Drizzle the ganache around the edges of the cake and fill in the top, smoothing with an offset spatula. Allow to firm for about 10 minutes.

Top with swirls of remaining frosting using a piping bag fitted with a closed star tip.

Garnish with halved Reese's and crumbled Reese's. Refrigerate until ready to serve. Serve at room temperature.