Roast the peppers by putting under broiler, turning frequently until skin is blackened & blistered. Place peppers in plastic bowl, with lid. When they are cool enough to handle, peel off the blackened part. With a sharp knife, make a slit in each pepper and seed it. Stuffing: Saute bell peppers in oil 5 minutes. Add mushrooms, S & P, saute 15 more minutes. Stuff into each poblano. Put in center of plate, pour shallot butter sauce over the top.