Trim and discard most of fat from beef, the place in 5 to 6 qt. pan with water. Cover and cood over med. heat for 30 min. Uncover and cook, turning as needed, until liquid evaporates and meat is well browned. In a bowl, combine vinegar, broth, chili powder and 1 tsp. of cumin; pour over meat. Continue cooking over med. heat until meat is very tender and apart easily. Let meat cool; shred and mix with pan juices. In lge. fry pan, combine 2 tbs. oil, onion, chiles, and remaining 1/2 tsp. cumin. Cook over med heat, stirring occasionally, until onion is soft. Stir in flour; then blend in 1 cup of the sour cream an stir until simmering. Remove from heat and blend in 1 cup of the cheese. Season to taste with salt. Set aside. In wide frying pan, heat 1/2" oil over med. heat. When oil is hot, add 1 tortilla at a time and cook, turning once, just until limp (10 seconds max.) Drain on paper towels and keep warm. Spoon 1/3 cup sour cream sauce and 1/4 cup shredded beef down center of each tortilla; roll to enclose. Set enchiladas, seam side down, in a 10 x 15 inch baking pan. Stop here if preparing for next day. Cover with plastic wrap and refrigerate. Bake uncovered in 375 F. oven until hot in center. Sprinkle with remaining 2 cups cheese evenly on top. Return to oven until cheese is melted. Use wide spatula to serve. Pass sour cream to spoon on individ. servings.