Combine celery and next five ingredients in a saucepan.
Bring to a boil, then simmer for 5 or 6 minutes.
Stir in a smooth mixture of the butter and flour; cook, stirring until thickened.
Pour into greased casserole; sprinkle crumbs over top.
Bake at 375F (190C) for 15 to 20 minutes, or until topping is browned.