Dice bacon and saute in large pot until translucent. Add onions, leeks and celery and saute for 5 minutes. Pour in 1 1/2 cups of juice and add potatoes and seasonings. Simmer until potatoes are tender about 10 minutes.
Melt butter in small saucepan. When it bubbles, add flour and cook 5 minutes, stirring often. This is called a roux. Roughly chop quahogs, reserving any liquid, add to pot and simmer for 2 minutes. Stir in roux and continue simmering another 5 minutes, stirring frequently.
In a separate pan, scald the cream by heating it until small bubbles appear around the edges of the pan. Do not boil. Stir cream into soup pot, mix together and remove from heat. Serve with a dollop of butter, oyster crackers and crusty bread.