1. In a large skillet, cook the ground beef over medium heat, breaking it apart with a spoon, until browned and fully cooked.
2. Drain any excess fat, then add the onion and garlic. Cook for 3-4 minutes until softened and fragrant.
3. Stir in the taco seasoning mix, tomato sauce, and diced green chiles. Let the mixture simmer for 2-3 minutes until well combined and heated through.
4. Remove the skillet from heat and stir in the shredded cheese until melted. If using refried beans, fold them in as well. Set the filling aside to cool slightly.

2. Assemble the Chimichangas:

1. Warm the tortillas in the microwave for 15-20 seconds or on a skillet to make them more pliable.
2. Place about ¼ cup of the beef and cheese filling in the center of each tortilla.
3. Fold in the sides of the tortilla, then roll it up tightly from the bottom to form a burrito-like shape. Secure the tortilla with a toothpick to keep it closed.

3. Fry the Chimichangas:

1. Heat about 1 inch of vegetable oil in a deep skillet over medium heat until it reaches 350°F (175°C).
2. Carefully place the chimichangas seam-side down in the hot oil, frying in batches if needed.
3. Fry for 2-3 minutes on each side, or until golden brown and crispy.
4. Transfer the chimichangas to a plate lined with paper towels to drain excess oil. Remove the toothpicks before serving.

4. Serve:

1. Top the chimichangas with your favorite toppings, such as sour cream, guacamole, salsa, shredded lettuce, diced tomatoes, and chopped cilantro.
2. Serve immediately and enjoy!