Heat oven to 375 degrees.
Butter a 1 1/2-qt. casserole.
Melt 2 tbsp. butter in saucepan.
Sprinkle in flour, salt and pepper and let bubble up.
Remove from heat.
Acd milk all at once.
Stir to blend.
Return to moderate heat and cook, stirring constantly, until boiling, thickened and smooth.
Remove from heat and stir in celery salt, parsley and potatoes.
Pour into prepared casserole.
Combine bread cubes and melted butter and sprinkle over potatoes.
Bake about 20 minutes or until hot and well browned.