Preheat the oven to 350°F. Heat a large skillet over medium high heat, then add just enough oil to barely coat the bottom of the pan. Add the tortillas, one at a time, and cook for about 20 seconds on each side until the tortillas are soft. Stack them on a plate as they are warmed. Add additional oil 1/2 teaspoon at a time as needed and keep going until all of the tortillas are softened.
Return the pan to the medium high heat, then add the beef and cook for about 4 minutes, breaking it up with a spoon, until it is browned and crumbly. Drain the beef in a colander.
Return the pan again to medium-high heat and add 1 tablespoon oil. When the oil is hot, add the onion and saute for 5 minutes until golden and tender.
Meanwhile, combine the enchilada sauce and chicken broth in a measuring cup.
Add the cooked beef to the pan with the onions, along with the scallions, jalapenos, green chilies and corn, plus 1 cup of the enchilada sauce mixture and stir to combine. Remove the pan from the heat, add ½ cup each of the Monterey Jack and the cheddar and stir to blend.
Pour ½ cup of the enchilada sauce mixture into the bottom of a 9 x 13 baking pan. Scoop ¼ cup of the filling mixture onto one of the tortillas and roll it up. Place the enchiladas seam side down in the baking dish, nestled closely to one another. Repeat with all of the tortillas and filling.
Pour the rest of the enchilada sauce mixture evenly over the enchiladas, and sprinkle the rest of the Monterey Jack and cheddar cheese over the casserole. Bake for 20 minutes until the filling is hot and the cheese is nicely melted. Serve hot.