Line one “jelly roll” pan with parchment paper cut exactly to fit the bottom of the pan, spraying the sides and bottom with nonstick spray before lining.
In a medium bowl, whisk the warm water with the cocoa powder until smooth. In a stand mixer fitted with the paddle attachment (or in a large bowl by hand), beat the sugar, oil, vanilla and eggs on medium speed until combined. Turn the machine to lowest speed and add the flour, baking soda and salt. Stir until just incorporated, but do not over mix! Stream in the cocoa power and water mixture and scrape the sides and bottom of the bowl. Stir in the buttermilk, the batter will be very thin. Spread the batter into an even layer making sure to get into the corners of the pan. Bake at 325 for 8 to 10 minutes until the cake is just barely baked through. If you over-bake it will be crispy. Let cool.
FOR THE FROSTING:
In a stand mixer, or by hand, beat together the cream cheese, peanut butter and powdered sugar until smooth. Add the whole milk and salt and mix until incorporated.
FOR THE GLAZE:
Gently melt the chocolate in a microwave safe bowl. Stir in the oil.
Place a wire cooling rack on top of a parchment lined jelly roll pan.
Drop the frosting in small dollops over the cake, then spread it evenly using an offset spatula. Remove the frosted cake from the pan and place on a cutting board, keeping the parchment attached.
Using sharp scissors, cut the cake horizontally into two strips. Cut each strip into 6 even sections. Using the parchment to help, turn the segments into a tight roll. Because the cake is pliable, you can mold it into a perfect log. Place the rolls seam side down on the wire glazing rack. Pour the glaze over each log and top with chopped peanuts, reusing the extra glaze that has dripped through the wire rack onto the parchment.