Creamy Ham and Potatoes

1. In a saucepan, melt margarine over medium heat. Stir in flour and then add cream of celery soup and water. Mix well.
   
2. Add mustard powder and pepper, reduce heat to low and simmer.
   
3. Slice red potatoes and onions. Layer into saucepan.
   
4. Dice ham and sprinkle over potatoes and onions. Cover tightly and cook over low heat.
   
5. After potatoes have been cooking for 15 minutes, preheat oven at 375 degrees.
   
6. Prepare crescent rolls according to package directions.
   
7. Bake for 10 to 15 minutes.
   
8. Garnish potatoes with cherry tomato slices, chives and grated mozzarella cheese.
   
9. Serve with crescent rolls.