Fill each tortilla with 1/2 cup cheese and 1 tablespoon scallion. Roll each and place in an 8-inch square dish. Melt 1/4 cup butter. Add 1/4 cup flour. Stir in 2 cups chicken broth until thick. Remove from heat and add 1 cup sour cream, 1 (4 ounce) can green chiles, seeded and chopped. Pour over the tortillas. Bake at 350 degrees F for 20 minutes.