Preheat oven to 375°.
Place bread in a food processor; pulse 10 times or until the coarse crumbs measure 4 cups. Set aside. Melt butter in a small skillet over medium heat; add shallot. Sauté 3 minutes or until soft (do not brown); stir in salt. Combine shallot mixture, milk, and next 5 ingredients (through egg yolks) in a large bowl; stir well. Add 3 1/2 cups bread crumbs; stir until well-blended.
Coat a 1 1/2-quart soufflé dish with cooking spray; sprinkle remaining 1/2 cup bread crumbs over bottom and sides.
Place egg whites and cream of tartar in a large bowl; beat with a mixer at high speed until stiff peaks form. Gently stir 1/4 egg-white mixture into shallot mixture; gently fold in remaining egg-white mixture. Spoon into soufflé dish. Bake at 375° for 1 hour or until soufflé is set. Serve immediately.