1Heat oven to 350°F. Spray 8-inch square pan with cooking spray. Cook and drain pasta shells as directed on package.
2Meanwhile, in 2-quart nonstick saucepan, heat oil over medium heat. Add onion; cook about 5 minutes, stirring frequently, until crisp-tender. Stir in beans, chili powder, cream cheese and 1/4 cup of the taco sauce. Reduce heat to medium-low; cook 2 to 3 minutes, stirring occasionally, until cheese is melted.
3Fill cooked shells with bean mixture. Place shells, filled sides up, in pan. Pour remaining 1/2 cup taco sauce over shells.
4Cover and bake 20 minutes. Sprinkle with shredded cheese and corn chips. Bake uncovered about 10 minutes longer or until cheese is melted. Garnish with sour cream and onions.