I don't know the comp rules, but I'd use it more for an inspiration. Brew a Chocolate peanut butter porter for the idea, then toss them in the mash to say you used them.
Yeah, the rules say I have to use the Reese's Puffs in the beer, but I can use any amount and I can use extracts if I want. But while the rules clearly say I can, it just doesn't seem in the spirit of the things to have the flavor come from extracts.