Cook pasta in boiling water 8 minutes; add broccoli. Cook 3 minutes or until pasta is done.
Drain.
Heat 2 teaspoons oil in a Dutch oven over medium heat.
Add garlic to pan; cook 45 seconds.
Transfer garlic mixture to a small bowl; set aside.
Add remaining 1 teaspoon oil to pan; stir in onion. Cook 1 minute, stirring frequently.
Remove from heat; stir in 3 cups milk. Lightly spoon flour into a dry measuring cup; level with a knife.
Combine the remaining 3/4 cup milk and flour in a small bowl, stirring with a whisk.
Add flour mixture to onion mixture. Return pan to medium-high heat, stirring constantly with a whisk; bring to a boil. Cook 1 minute or until thick, stirring constantly with a whisk.
Remove from heat; stir in the cheeses, salt, black pepper, red pepper, and nutmeg.
Add pasta mixture to milk mixture, tossing gently to coat.
Pour mixture into a 13 x 9-inch baking dish coated with cooking spray.
Combine garlic mixture and bread in a food processor; pulse 15 times or until fine crumbs measure 1 cup.
Sprinkle breadcrumb mixture over pasta mixture.
Bake at 400 for 18 minutes or until the top is brown.