Heat half cup of the stock in a large saute pan and add the onions. Simmer, covered, until onions are tender, 10 to 15 minutes. Add the mushrooms and simmer for 5 minutes, stirring occasionally. Stir in the paprika, cayenne, lemon zest, and the remaining stock and simmer briskly for about 10 minutes until reduced by one-third ( 0.33333333333333). Season to taste with salt and pepper. Remove the pan from the heat, let the mixture rest for about 5 minutes, and then swirl in the yogurt. Sprinkle with chopped dill or parsley. Serve with slices of baked polenta, steamed brown or wild rice, or noodles. Serves 2 to 4. From Eat More, Weigh Less by Dean Ornish, M.D. Formatted for MM:dianeE