Potato Leek Soup

INGREDIENTS

• 1 small bay leaf
• 2 sprigs fresh flat-leaf parsley
• 10 whole black peppercorns
• 2 tablespoons unsalted butter
• 1 tablespoon olive oil
• 3 leeks, white and light-green parts only, cut into 1/2-inch pieces
• 2 shallots, finely chopped
• 1 pound potatoes, peeled, cut into 1/2-inch dice
• 1 quart homemade or low-sodium canned chicken stock
• 1/2 cup milk
• 1/4 cup heavy cream
• Coarse salt and freshly ground white pepper
• Fresh chervil, for garnish