Carve off the outer bit of your celeriac with a knife (it’s too tough for peelers). Cut into a 3 cm dice. Thinly slice your celery. Peel and finely chop your onion. Peel and chop your garlic. Finely chop the
leaves from your rosemary.
Get a large pot hot. Add 1 tbsp of oil. Add your veg. Season well. Sizzle for 5 mins, so there’s a hint of colour to the veg. Add the orange zest and juice.
Cook the veg till it has a sticky glaze. Pour in enough stock or water to cover. Bring to the boil. Lower heat. Simmer till all the veg is soft, about 20 mins.
Blend the soup till smooth. Add more boiling water or stock till it’s as thin as you like. Taste. Tweak seasoning. Sizzle a few rosemary leaves till just crisp. Scatter over the top. Serve.