Drain the oysters and reserve the liquor. Add enough water to liquor so that it equals one cup and set aside. Melt the butter in a medium saucepan or small stockpot. When the foam subsides, add the onions and cook, stirring, until soft. Stir in oyster liquor/water mixture, milk and cream and bring to a simmer. Add the oysters and simmer until they curl. Season with salt and pepper. Garnish with oyster crackers.
Makes about 5 cups