Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan. In a large mixing bowl, sift together all-purpose flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt until well combined. In another bowl, whisk together eggs, buttermilk, hot water, vegetable oil, and vanilla extract until smooth. Gradually pour the wet ingredients into the dry mixture and blend until just combined and smooth, then pour the batter into the prepared pan.

Place the cake in the preheated oven and bake for 35–40 minutes, or until a toothpick inserted in the center comes out clean. Allow the cake to cool completely in the pan on a wire rack.

Once the cake has cooled to room temperature, poke holes all over the surface of the cake approximately every 1 inch apart.

In a saucepan over low heat, combine smooth peanut butter, sweetened condensed milk, and whole milk. Stir continuously until the mixture is smooth. Pour it evenly over the poked cake.

In a chilled mixing bowl, whip heavy whipping cream until soft peaks form. Gradually add powdered sugar, peanut butter, and vanilla extract, continuing to mix until stiff peaks form.

Spread the prepared peanut butter whipped cream over the entire surface of the cake. Garnish with chopped chocolate peanut butter cups and a sprinkle of peanuts.