Heat oven to 425 F. Lightly grease a 2 1/2-quart baking dish.

In a medium saucepan, melt the butter. Add onion and celery and cook for 5 to 7 minutes or until softened.

Add the flour to the saucepan and stir until blended. Continue to cook, stirring, for 2 minutes. Add the chicken broth and cook, stirring, until thickened.

Stir in marjoram and salt and pepper, to taste. Add peas and carrots or peas or green beans, chicken, and ham.

Spoon the mixture into the prepared baking dish. Spoon hot mashed potatoes evenly over the top and spread gently to cover. Put the baking dish on a foil-lined baking pan to catch any drips.

Bake the pie for about 20 minutes, or until hot and bubbly. To brown the potatoes a little more, turn the broiler on for a minute or two.