1. Place a small roasting pan in oven. Preheat oven to 450°.
2. Remove hot pan from oven; melt butter in pan. Add squash and next 3 ingredients (through shallot) to pan. Sprinkle squash mixture with 1/4 teaspoon salt and pepper; toss. Bake at 450° for 20 minutes or until tender, turning once. Cool squash mixture. Place squash mixture in a food processor; process until smooth. Scrape squash mixture into a bowl.
3. Reduce oven temperature to 425°, and place a rimmed baking sheet in the oven.
4. Place the French bread in a food processor, and pulse 10 times or until fine breadcrumbs measure about 1/2 cup. Lightly coat 5 (8-ounce) soufflé ramekins with cooking spray; sprinkle crumbs evenly over dishes.
5. Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and the remaining 1/4 teaspoon salt in a medium, heavy saucepan over medium heat. Gradually add milk, stirring constantly with a whisk; bring to a boil. Cook 1 minute or until thick and bubbly. Remove from heat; let stand 5 minutes. Add cheeses; stir until smooth. Stir in squash mixture and egg yolks.
6. Place egg whites in a large mixing bowl; beat with a mixer at high speed until medium peaks form (do not overbeat). Gently stir one quarter of egg whites into squash mixture; gently fold in remaining egg whites. Divide mixture evenly among prepared dishes. Sharply tap dishes on counter 2 to 3 times to level. Place dishes on preheated baking sheet; place in 425° oven. Immediately reduce oven temperature to 350°. Bake soufflés at 350° for 45 minutes or until golden, puffed, and set. Serve immediately.