Melt the butter in a large saucepan over medium-low heat. Add the onion, cook for 5 minutes until translucent. Sprinkle the onion with flour and stir in the potatoes, chicken stock, milk and celery seed. Heat to boiling, reduce the heat. Cook over medium-low heat covered for about 25 to 30 minutes until potatoes are tender.

Stir the mustard and paprika into the chowder. Cook uncovered for 5 minutes. Remove from heat, stir in the grated cheddar and season with salt and pepper to taste.

Pour into bowls and shred some sheddar on top and serve. Crackers or French bread on the side is nice addition.