Prepare the Filling:In a large skillet over medium heat, brown the ground beef until fully cooked. Drain excess fat.Add chopped onion and garlic to the beef and sauté for 3–4 minutes until softened.Stir in taco seasoning, tomato sauce, and green chiles. Let simmer for 2–3 minutes.Remove from heat and mix in shredded cheese until melted. Stir in refried beans if using. Let the mixture cool slightly.
Assemble the Chimichangas:Warm tortillas in the microwave or skillet until pliable.Spoon about ¼ cup of filling into the center of each tortilla.Fold the sides inward and roll up tightly burrito-style. Secure with toothpicks to keep them closed during frying.
Fry the Chimichangas:Heat 1 inch of vegetable oil in a deep skillet over medium-high heat until it reaches 350°F (175°C).Carefully place each chimichanga seam-side down in the hot oil.Fry for 2–3 minutes on each side until golden brown and crispy.Remove and place on a paper towel-lined plate. Remove toothpicks before serving.
Garnish and Serve:Top your hot chimichangas with sour cream, guacamole, salsa, shredded lettuce, diced tomatoes, and chopped cilantro as desired.