Peel yams and slice into 1" pieces.  Place in pot and bring to boil.  Simmer on medium for 5 minutes or until tender.  Drain and place yams in baking dish.

Clean swiss chard, remove ribs and coarsely chop the greens.  Saute briefly in yam pot and add to baking dish.

Melt butter in a small saucepan, add flour and whisk until blended. Let (the roux) cook for a few minutes.  Add milk and continually whisk until thickened (into a bechamel sauce).  Season with salt and pepper

Place cooked yams in baking dish.  Place cooked chard over yams.  Pour milk mixture (or bechamel sauce) over veggies. Top with grated cheese and breadcrumbs.  Bake at 350 degrees for 20 minutes or until top is browned.