PLACE FLOUR IN A MIXING BOWL and slowly pour in the beer while mixing. Add the egg white, pepper and desired salt and mix well. Taste for salt and pepper and add if desired. Cover the bowl and set aside for 30 minutes before using. Combine onions and oil in a small Dutch oven or casserole, place in the oven and turn temperature to 190ºC . If using fresh plum tomatoes, bring a pot of water to the boil, plunge in the plum tomatoes and cook a minute or so, until the skins crack. Drain tomatoes and when they are cool enough to handle, peel them. Discard peels, cut tomatoes in half crosswise and squeeze out seeds. Add tomatoes to the Dutch oven. Remove stems from the dried chili peppers and remove the seeds. Add peppers to the Dutch oven. Add cumin, cream and salt as desired. Cook 30 minutes, remove from the oven and scrape the contents into a blender or food processor. Blend until smooth and set aside. Meanwhile, place a piece of cheese under the skin of each breast, dredge each breast in flour and shake off the excess. Heat the oil in a heavy skillet over medium heat on the stove. When the oil is hot enough for frying (350F), dip each breast in the beer batter and let the excess run off. Place skin-side down in the oil and fry until golden. Turn and fry other side, about 1 minute per side. Remove breasts from the oil as they are done, drain on paper towels and transfer to a baking dish. Place the chicken breasts in a preheated 190ºC oven for 15 minutes. Place tomato sauce in a saucepan and reheat. (If the mixture is too thin, place it in a saucepan over high heat and boil down.) Pour the sauce onto a platter and arrange the chicken breasts on top.