Roasted Beet Soup with Crème Fraîche

1 1/2 teaspoons butter

1 1/2 teaspoons olive oil

1 leek (white and pale green parts only), chopped

1 small onion , thinly sliced

1 celery stalk, chopped

teaspoon ground ginger

teaspoon ground allspice

teaspoon ground white pepper

2 cups water

1 small bay leaf

1 fresh thyme sprig

1 fresh parsley sprig

1/4 cup whipping cream

2 tablespoons creme fraiche or sour cream