This old-fashioned, potluck dish is a great cold-weather meal: Its quick, easy to fix and hearty without being heavy.
Cook spaghetti according to package directions, omitting salt. Lightly coat 10-inch deep-dish pie plate or ovenproof casserole with cooking spray. Drain pasta; arrange in pie plate or casserole, forming crust. Set aside.
Preheat oven to 350°F. In large skillet, heat oil over low heat. Add onion, garlic and bell pepper. Cook, stirring often, until onion is softened, about 3 minutes. Sprinkle vegetable mixture with flour. Cook, stirring, 1 minute. Remove skillet from heat. Whisk in milk, a little at a time. Return skillet to medium-low heat, stirring until sauce thickens. Remove from heat; add spinach. Cool mixture slightly; stir in herb mix and egg substitute. Pour mixture into pasta crust and sprinkle top with cheese.
Bake until filling is set and heated through, about 30 minutes. Serve hot.