Mushroom soup with herbed creme fraiche

Ingredients

• Mushroom soup
• 80 gram butter
• 3 french shallots, chopped finely
• 1 trimmed celery stalk, chopped finely
• 2 cloves garlic, crushed
• 400 gram flat mushrooms, chopped finely
• 300 gram button mushrooms, sliced thinly
• 200 gram swiss brown mushrooms, sliced thinly
• 1/3 cup (80ml) dry sherry
• 1.5 litre (6 cups) salt-reduced chicken stock
• salt and freshly ground black pepper
• Herbed creme fraiche
• 200 millilitre carton creme fraiche
• 2 tablespoon chopped flat-leaf parsley
• 1 tablespoon chopped fresh chives
• 1 tablespoon chopped fresh chervil