Divide chicken and 1/4 tsp cheese among the 8 tortillas. Place in 9x13 lightly sprayed baking pan, seam side down.
Sauté onions in vegetable oil, add melted butter, gradually whisk in and brown flour, add chicken broth and bring to a boil, remove from heat and add sour cream and green chili. Pour over tortillas, sprinkle with remaining cheese and jalapeños if you want spicy. Jalapeños are optional.
Bake at 400 degrees for 25 minutes