Preheat oven to 350°
In the bowl of a mixer combine sugar and eggs and mix on medium speed to combine completely.
Add in flour, baking powder and mix just until folded in.
Then add in milk, butter, oil, peanut butter, and vanilla mix on low until it won't splatter, then increase speed to medium until everything is mixed well about one minute.
Prepare a 13x9 baking pan with a baking spray like Baklene or use shortening and flour. (this will ensure the cake will release easily).
Pour the batter into the pan and bake for 30-40 minutes or until a toothpick comes out clean.
Cool the cake for 15 minutes, then turn out the cake onto a cooling rack to cool completely.
Once the cake is cooled completely, slice the cake in half lengthwise so you'll have two even layers.
*While the cake is baking prepare the fudge filling and frosting.