Preheat your oven for the temperature on the Pillsbury cake mix. Meanwhile, mix the cake batter according to the directions.
Grease your chosen cake pan,(I used a large round pan)and lightly grease it and dust with flour. Pour entire contents of cake batter into the pan. Bake until done, usually 25-35 minutes.
Once cake is fully baked remove from oven and place on a cooling rack for 30 minutes. Then, gently place a hand on the center of cake and flip the cake upside down allowing the cake to come out of the pan with ease. Once cake is sitting on your hand, bring the platter or cake stand and place it upside down on to the bottom of the cake, then flip the cake back up right. Now you can ice the cake and add the Reese's pieces and chocolate sprinkle.