Heat oven to 375°F.
In large bowl, combine chicken, 1/4 cup tomatillo sauce, 1/2 cup shredded cheese and the chiles.
Wrap tortillas in damp paper towels. Microwave on high 1 minute.
Spread 1/2 cup tomatillo sauce over bottom of flame-proof baking dish. Dip 1 tortilla in a bowl of warm water, shaking off excess. Top with about 1/3 cup chicken mixture; roll up and place seam-side down in baking dish. Repeat with remaining tortillas and filling, fitting tightly into pan.
Stir sour cream into remaining tomatillo sauce. Spread on enchiladas. Top with remaining cheese.
Bake in 375°F oven for 20 minutes or until heated through. If desired, place under broiler to brown, about 2 minutes.
Meanwhile, prepare rice and beans following package directions. Serve with enchiladas.