Place clams and 1/4 cup water in lg pot. Cover, cook on high until clams open. Transfer clams to a bowl. Strain the liquid to remove grit. Add enough water to clam liquid to measure 2 cups.
Remove clams from shells and coarsely chop. Heat oil in lg heavy pot over medium heat. Add bacon and cook until crisp. Drain on paper towels. Add onion and potatoes to pot. Cook 5 mins.
Stir in flour, cook 2 mins, stirring. Stir in clam juice and milk. Season w/ salt and white pepper. Cover, reduce heat and simmer 20 mins. Stirring occasionally, until potatoes are tender. Stir in heavy cream and clams. Heat through. Sprinkle w/ bacon and parsley.