If desired, the sauce for this dish can be thickened just prior to serving by quickly stirring in 1 TBS cornstarch dissolved in 3 TBS water.
Place mushrooms in food processor and mince. Remove to mixing bowl. Cut chicken breasts into pieces, place in food processor and mince. Add to mixing bowl, along with bread crumbs, onion, pepper, salt and egg. Combine ingredients with hands and shape into eight equal-sized patties. Place flour on waxed paper and use to coat patties.
In large skillet, over medium heat, melt 2 TBS butter. Add celery and cook just until crisp-tender. Place celery around the edge of a warm platter. To skillet, add remaining butter and, over medium-high heat, saute chicken patties, turning occasionally, for 10-12 minutes (or until brown on both sides). Remove patties to center of heated platter. Add cream to pan, bring to a boil and stir until heated through. Season with salt and pepper. 4 servings.