- 3 cups chopped Vidalia onions, about 3 large onions (or any sweet onion)
- 1/2 teaspoon dried leaf thyme
- 1 teaspoon dried parsley flakes or 1 tablespoon fresh chopped parsley
- dash crumbled rosemary
- 2 tablespoons butter
- 2 tablespoons flour
- 1 1/2 cups milk
- 1 cup plain soft bread crumbs, divided
- 1 tablespoon butter, melted
- 2 eggs, separated
- 1/2 teaspoon salt
- 1/8 teaspoon pepper
- dash ground nutmeg, optional
- fresh chopped parsley, optional
Butter a 1 1/2-quart casserole. Heat oven to 350° F. Beat egg whites in a medium bowl (not plastic) until stiff peaks form; set aside. Lightly beat the egg yolks in a small bowl; set aside.
In a saucepan, combine the chopped onions, thyme, 1 teaspoon parsley flakes or 1 tablespoon fresh chopped parsley, and rosemary. Add about 1 cup water; cover and bring to a boil. Reduce heat and continue boiling until onions are tender; drain well.
In a medium saucepan, melt butter; stir in flour until well blended. Gradually add milk, stirring constantly. Cook over medium-low heat, stirring constantly, until thickened. Add the drained onions and 1/2 cup of the soft bread crumbs. Quickly stir in the slightly beaten egg yolks; add salt, pepper, and a dash of nutmeg, if desired. Fold in the stiffly beaten egg whites until well incorporated. Turn into prepared casserole.
Toss remaining 1/2 cup bread crumbs with the melted butter and fresh chopped parsley, if using. Sprinkle over the onion mixture. Bake for about 40 to 50 minutes, or until a knife inserted in center comes out clean.