Preheat oven to 375°.
Melt butter in a medium nonstick skillet over medium-high heat. Add green onions, and sauté 4 minutes. Combine onion mixture, breadcrumbs, and next 6 ingredients (breadcrumbs through egg yolks) in a large bowl. Beat egg whites and cream of tartar at high speed of a mixer until stiff peaks form. Fold egg white mixture into breadcrumb mixture; spoon into a 2-quart soufflé dish coated with cooking spray. Bake at 375° for 1 hour and 5 minutes or until set. Serve immediately.