Peel and cut potatos; set to boil. While those are boiling, cube chicken breast and put into a 9 inch (metal) pie plate. Preheat oven to 350°F.
In a skillet add carrots, broth, cream and seasonings (feel free to change seasoning to your taste). Cook over medium-high heat for 2.5 minutes; add celery, stir. Cook another 2.5 minutes. *At this point if the sauce is too runny, make a rue with flour and just enough water to make a runny paste. Add it 1 teaspoons at a time until the sauce seizes up* Pour over chicken.
When potatos are tender, mash with sour cream and margarine and salt if you like. Spoon potatos over chicken/veg. and spread around until it's all covered up.
Bake in the oven for 10 min's -- take out and add cheese to top, put back in oven till cheese is melted. Serve hot!