Cook and bone 1 chicken; cut into pieces. Place 1 package Dorito's in bottom of 9 x 13 inch cake pan. Cover with chicken pieces. In another pan, saute 1 large onion in 1/4 cup butter. Add 1 can Cheddar cheese soup, 1 (8 ounce) can enchilada sauce, and 1 can cream of chicken soup. Pour over chicken and chip. Top with 1 cup grated Velveeta cheese. Cover with foil and bake 30 minutes at 350 degrees