When cake is finished baking, immediately poke holes all over the top using the back of a wooden spoon.
Add peanut butter to a microwave safe bowl and microwave on high for 45 seconds, or until peanut butter is thin.
Stir in ½ cup of candy pieces.
Pour peanut butter mixture over top of the cake, using a spatula to spread it evenly.
Allow to cool.
In a large bowl, mix whipped topping and chocolate syrup; spread on top of cooled cake.
Top with remaining candy pieces.
Christina's Notes
Chocolate: Add chocolate chips to the cake batter for more chocolate flavor.
Crunchy Peanut Butter: Crunchy peanut butter can be a replacement for creamy peanut butter.
Different Flavors: Make with a white or yellow cake mix if you prefer. You could also make a chocolate cool whip with cocoa powder in regular cool whip.
Cupcakes: Poke a hole in the middle of each cupcake for the peanut butter filling.