Put potatoes in a large saucepan with 3 cm cold water and 1 teaspoonsalt; bring to a boil.

Cover, reduce heat and simmer 25 minutes, until potatoes are tender;drain and cool.

Peel potatoes and slice 1 cm thick; set aside.

Heat oil in a medium-size skillet; saute onion until soft.

Stir in flour, mustard, celery seed and remaining one third teaspoon salt.

Gradually add half cup water and vinegar; cook over low heat, stirringconstantly, until mixture boils and thickens.

Combine potatoes, green pepper and carrots in a bowl; add sauce, mixingwell.

Spoon half the mixture into a shallow 8x8-inch baking dish; sprinklewith half cup cheese.

Cover with remaining potato mixture and cheese.

Bake, uncovered, in preheated 350'F. oven 15 to 20 minutes, or untilcheese is melted and vegetables are hot.