Jerusalem artichoke, celeriac and orange soup with gremolata

This velvet potage is deceptive. It tastes so creamy but does not have a drop of dairy in it.

Soup:

2 Tbsp	Olive oil
1	Onion, chopped
750 g	Celeriac, peeled and diced
500 g	Jerusalem artichokes (Main)
1 ½ Ltr	Vegetable stock
½ tsp	Saffron threads, soaked in a little hot water (optional)
1 Tbsp	Honey
1	Orange, grated zest and juice

Gremolata:

1 clove	Garlic
1 handful	Flat leaf (Italian) parsley
1	Orange, zest

Directions

1. Heat the oil in a saucepan, add the onion and cook until softened.
2. Add the celeriac, cover and cook for 10 minutes, stirring occasionally.
3. Add the remaining ingredients. Bring to the boil, then simmer for 20 minutes until the vegetables are tender.
4. Transfer the contents of the pan to a blender in batches and liquidise to a smooth purée. For the gremolata garnish, finely chop all the ingredients and mix together.
5. To serve, ladle the soup into bowls and spoon over the gremolata.