Heat oil in a very large skillet or pot over medium-high heat.
Add the onions to the hot oil and cook for 3-4 minutes, just so they begin to soften. Add the diced green chilies and saute for another minute.
Sprinkle the flour, salt, cumin and garlic powder over the onions and chilies and cook for another minute, stirring to combine and prevent burning.
Add the shredded meat, green chili salsa, and beef broth. Cook, stirring occasionally, for about 5 minutes, giving the mixture time to thicken a bit and for the meat to absorb some of the salsa and broth. Taste and adjust salt, if necessary. Remove from heat.
Warm the tortillas in the microwave between two damp paper towels for one minute so they are pliable and easy to work with.
Working with one tortilla at a time, fill with a good amount of the chimichanga shredded beef. The exact amount will depend on the size of tortillas you have but you want to be able to wrap the tortilla around the meat to create a tight burrito-like packet. When I use regular size tortillas, anywhere from ¾ to 1 cup of the shredded beef mixture is about right.
Fold both sides of the tortilla in towards the middle, then fold the bottom side over and roll the chimichanga up, creating a tight burrito-like packet with all of the meat securely enclosed inside the tortilla. Secure with a toothpick or two to create each chimichanga and hold it together. Repeat with remaining tortillas and shredded beef.
When ready to begin frying, pour enough oil into a large skillet to cover the bottom of the pan by about an inch. Heat over medium-high heat until oil begins to shimmer (about 350 degrees if you have a thermometer to set in the oil). Working in batches of 2-3 chimichangas at a time, carefully place each chimichanga into the hot oil, seam side down, using the tongs and cook, turning occasionally to brown and crisp the chimichanga on all sides, about 4-6 minutes, total.
Remove each chimichanga from the hot oil and transfer to a wire rack lined with paper towels, allowing any excess oil to drip off before transferring to a serving platter or individual plates. Repeat with remaining chimichangas, replacing the oil in the pan and bringing it up to temperature if needed, until all chimichangas have been fried.
Remove all toothpicks and serve with sour cream, guacamole, shredded cheese, tomatoes, lettuce and salsa or pico de gallo.