I've only done one chocolate peanut butter and also used pb2. It came out great! I'll write up the recipe as soon as I find my log book. Basically added cocoa powder during boil and racked onto pb2 in secondary. Nice chocolate sweatiness up front with a lingering peanut butter flavor. We also back sweetened with a tad of sweet n low at bottle time to counteract the peanut bitterness.
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