Pureè of Winter White Vegetables

Ingredients

• 6 parsley stems
• 1 bay leaf
• 2 baking potatoes, about 1 1/2 pounds, peeled, coarsely chopped
• 2 pounds celery root, peeled, coarsely chopped
• 3 medium turnip, peeled, coarsely chopped
• 10 cloves garlic
• 1 yellow onion, peeled, quartered
• 3 leeks, white and 1" of the green only, coarsely chopped and washed well
• 2 sprigs fresh thyme
• 2 tablespoons heavy cream or milk
• 3 tablespoons butter, cut into 6 pieces
• 1 teaspoon white wine vinegar
• 2 tablespoons chopped parsley
• Salt and freshly ground black pepper