Enchilada sauce: Melt butter in medium saucepan, saute onion and garlic in butter until tender. Add tomato sauce, chiles, sugar, cumin, salt, oregano and basil. Simmer on stovetop about 20 minutes, until heated though and well blended.
Fill each enchilada with 1/3 cup chicken and sprinkle with 2 T cheese, roll and place seam side down in lined 9x13. Blend sour cream with enchilada sauce and pour over enchiladas. sprinkle with remaining cheese.
Thaw completely. Bake uncovered at 350 for 40-50 minutes.