Roast the poblanos over a gas flame, turning until blistered and slightly charred all over. Put them in a heavy plastic bag and set aside to steam for 10 to 20 minutes. Peel the skin. Carefully make a lengthwise slit in each of the peppers and remove the seeds and membranes. Rinse and drain well using paper towels pat the peppers dry.
Heat oil in a large skillet or saucepan, add meat and brown. Add chopped onion, and garlic stirring for one minute. Add tomatoes, salt, cumin and black pepper and cook for 10 to 15 minutes. Stir constantly until meat stuffing is dry. Set aside to cool.
Stuff the peppers with the filling and secure with a toothpick.
In a bowl beat egg whites until stiff and foamy. Add egg yolks to egg whites and blend.
In a separate bowl add flour for dusting peppers and set aside.
In a deep skillet heat the oil. Batter and flour dust peppers and drop into hot oil. Fry to a golden brown on both sides. Lay peppers on paper towels to soak up excess grease. Serve chili rellenos topped with Ranchero Sauce, garnished with shredded queso blanco and chopped cilantro.
In skillet heat oil until hot. Brown onion, garlic, peppers, and tomatoes for 2 minutes or until transparent. Add the tomatoes and cumin, and simmer for 10 to 15 minutes until sauce is lumpy. Set aside.