Barbara's Potato Bake

3 med potatoes, peeled, cut into sm wedges
1 sm bunch of fresh broccoli, cut into flowerets
1 white onion, sliced
Water
Salt

Topping:
3/4 cup mayonnaise
1/4 cup tomato ketchup
1/2 cup half and half
1 tbsp mustard
1/2 cup cheddar cheese
2 tbsp Parmesan cheese

Place potatoes in a large saucepan.  Cover with water.  Add a little salt.  Bring to a boil
and simmer for about 12 minutes.  Add broccoli flowerets and sliced onion.  Simmer for
another 8 minutes until vegetables are tender, but not mushy.  Drain well.  Place potato
mixture in a lightly greased shallow baking dish.  For topping, combine mayonnaise,
tomato ketchup, half and half and mustard.  Spread evenly over top of vegetables.  Sprinkle
with cheeses.  Bake at 375 to 400* until hot and the cheeses are melted.