Preheat oven to 375°.
Cut a piece of foil long enough to fit around a 1-quart soufflé dish, allowing a 1-inch overlap; fold foil lengthwise into thirds. Lightly coat one side of foil and bottom of dish with cooking spray. Wrap foil around outside of dish, coated side against dish, allowing it to extend 4 inches above rim to form a collar; secure with string or masking tape.
Heat oil in a small skillet over medium-high heat. Add onion and garlic; sauté 2 minutes or until tender.
Combine onion mixture, thyme, salt, pepper, beans, and egg substitute in a blender or food processor; process until smooth. Spoon mixture into a large bowl. Stir in cheese; set aside.
Beat egg whites and cream of tartar at high speed of a mixer until stiff peaks form. Gently stir one-fourth of egg white mixture into bean mixture. Gently fold in remaining egg white mixture.
Pour mixture into prepared soufflé dish. Bake at 375° for 1 hour or until puffed and golden. Carefully remove foil collar, and serve immediately.