In a skillet melt bacon grease over medium heat. Saute meat, onion, garlic, tomatoes, chilies and potatoes until the onion softens. Add salt, oregano, chili powder and cilantro; simmer 2-3 minutes. Place a scant 1/2 cup meat filling on each tortilla. Fold envelope-style, like a burrito. Fry seam side down, in 1/2 inch of hot oil (360-375~F) until crispy and brown. Turn, and brown other side. Drain briefly on a paper towel. Place on a serving plate and top with shredded cheese, a dollop of sour cream and salsa. Place shredded lettuce next to chimichanga and top with tomatoes. Serve immediately.