Peel and slice kohlrabies.
In covered saucepan cook kohlrabies in small amount of boiling salted water 15 minutes.
Add) carrots; cover and continue cooking till vegetables are tender, 10 to 12 minutes more.
In saucepan cook onion in the 2 tablespoons butter till tender but not brown.
Blend in flour, salt, and dash pepper.
Add milk all at once.
Cook and stir till thickened and bubbly.
Stir in cooked vegetables parsley, and lemon juice.
Turn into 1-quart casserole.
Com bine bread crumbs and the 1 tablespoon melted butter; sprinkle around edge of casserole.
Bake at 350° till heated through, 20 to 25 minutes.