In a large mixing bowl, combine the cooked, shredded chicken, refried beans, shredded cheese, diced onion, ground cumin, chili powder, salt, and pepper. Mix until well combined.
Place tortillas on a flat surface. Spoon an equal amount of the chicken filling into the center of each tortilla.
Fold in the sides of the tortilla, then roll it up tightly from the bottom to create a burrito shape.
Heat vegetable oil in a deep fryer or heavy pot to 350°F (175°C).
Carefully place the chimichangas in the hot oil, seam side down. Fry until golden brown, about 3-4 minutes on each side.
Remove the chimichangas from the oil and place them on a plate lined with paper towels to drain excess oil.
Allow them to cool slightly before serving. Serve with salsa, guacamole, or sour cream if desired.
You can customize the filling by adding other ingredients like bell peppers or corn.
For a healthier version, consider baking the chimichangas instead of frying them. Brush with a little oil and bake at 400°F (200°C) for about 20 minutes or until golden brown.