Fenland Celery Soup - Lavender and Lovage

Ingredients

• 1 medium head of Fenland or British Celery (trimmed and the branches finely chopped)
• 1 small onion, peeled and finely chopped
• 40g butter (I use salted butter)
• 750mls vegetable stock (I use Marigold Swiss vegetable bouillon powder)
• 1/2 pint of milk
• 1/4 teaspoon celery seeds
• celery salt
• white pepper
• some celery leaves, trimmed form the celery branches (for a garnish)