Preheat oven to 350 F. Grease and flour two 9 in cake pans.
In a saucepan, mix sugar, cocoa, baking soda, salt, and coffee granules. Meanwhile in another saucepan bring 1 cup of water to a boil.
Pour the boiling water into the sugar-cocoa mixture, stirring constantly. Place on the burner and bring to a boil. As soon as it boils remove from heat and let it cool in the saucepan for about 10 minutes.
After the 10 minutes are up. Pour the mixture into the bowl of a stand mixer. Add the oil, vanilla and mix on low speed.
Add the flour and mix on low speed until it is just incorporated. Finally, add the egg yolks, eggs, and buttermilk, mixing on low speed.
Pour the batter into the prepared pans, bake for 23-26 minutes until the cake spring back when lightly touched.
Remove from the oven and let cool in the pans for about 10 minutes, before cooling completely on a plate.
To make the frosting, beat the butter on medium-high speed for 2 minutes in a stand mixer until white and fluffy. Add the peanut butter and beat for another minute.
Gradually add the powdered sugar, beating until smooth. Add enough milk until the frosting is a nice spreading consistency.
To assemble the cake, place one layer on a serving platter, Spread about a half cup frosting on the top and then place the second layer on top.
Finish frosting the cake with a knife and garnish with Reese's if desired.