Directions

1. Preheat oven to 400°F.
2. In a small saucepan, cook onions in 1 tablespoon of butter for two minutes or until tender. Stir in the cream, mustard and remaining butter, add salt and pepper to taste. Bring to a boil. Reduce heat; simmer, uncovered, for 5 minutes.
3. Reduce heat to low; stir in half of the cheese until melted. Remove from the heat. In a greased shallow 2-1/2 quart baking dish, layer a third of the potatoes; top with a third of the sauce. Repeat layers twice; sprinkle with remaining cheese. Top with mustard seed.
4. Bake uncovered for 30 minutes. Cover and bake 25-30 minute longer or until potatoes are tender. Let stand for 5 minutes before serving.