The delicious, earthy flavours of celeriac, thyme and truffles compliment each other perfectly in this beautifully smooth and sophisticated soup
There's just something about the flavour of certain root vegetables. They have a real, rich, earthy depth to them which is complimented by so many other flavours and celeriac is possibly my favourite of them all.
I chose to use fresh, young thyme leaves in this - adding most at the beginning to meld in with the other flavours during cooking, and then a few more leaves at the end to add that beautiful fresh-picked taste, together with just a little scattering on top, and a luxurious drizzle of extra truffle oil on the top (well, I do have a big bottle bought for me last Christmas by my children which I realised needs using up!). It would have been amazing to have shaved some fresh truffle over the top, and maybe a little blended into the soup right at the end, but one must save these luxuries for special occasions (or find an amenable pig and an appropriate area in the woods to find one's own truffles...still, there's nothing stopping you doing this if you want to impress your guests!).
I think crispy pancetta, would make a delightful topping too, sprinkled on right at the end. To be honest, I was *this* close to doing so, but I thought it might not look quite so pretty and refined in the photo - but go on... do it to yours, it will taste delicious! (Unless you're a vegetarian, of course!).
Makes around 2 litres of soup, hence 8-10 servings. From 63 calories per skinny portion (for a tenth using 300ml extra stock at the end instead of cream and milk), to 152 calories for an eighth of the full fat version. [Calories in square brackets].
If making in a Thermomix, it is important to weigh the vegetables as this will take it to maximum capacity. If making in a pan, you can be a little more laissez-faire with your ingredients as you don't have to conform to the rather splendid logic of German technology.
- 650g celeriac (around 2 small-medium after peeling) 
- 2 cloves garlic 
- 1 medium onion (100g after peeling etc.) 
- 6 sprigs young, tender thyme (less if woodier with lots of tiny leaves on it) 
- 15g butter or 1 tbsp oil (if avoiding dairy/vegan, e.g. a mild olive oil) 
- 200g floury potato (e.g. Maris Piper, King Edwards etc. 2 medium, after peeling) 
- 850ml stock (chicken being my first choice, or vegetable) 
- 100ml double (heavy) cream* 
- 200ml milk (full fat)* 
- 1 tsp to 1 x 15ml tbsp truffle oil, to taste [45-135]
- Salt to taste
- Pepper to taste (you can either use freshly ground black pepper, which is my preference for flavour, or if you want to preserve the clean look of the soup, you could use white pepper, but I am not a huge fan of the flavour myself) 
*If you want to avoid dairy / cook vegan, or reduce the calories just use additional stock, hot water or nut / rice milk at the end to thin the soup to your desired texture.
A few fresh thyme leaves
A drizzle of truffle oil (or cream), per bowl, from a teaspoon
Crispy pancetta or bacon
Truffle shavings (if you're really posh!)
Curly strips of deep-fried celeriac crisps (if you have the time!)
(See below for Thermomix method)
Peel the celeriac and potato and cut into 1 inch dice. To prevent the celeriac from browning, put a little lemon juice into a bowl of cold water, and toss the celeriac in as you go (if you want to shorten the cooking time to about 20 minutes, you can put larger chunks into a food processor and pulse them to give a smaller dice). Chop up the onion and garlic, and then sautee gently in the butter with the leaves from 3/4 of the thyme in a large pan for five minutes or so until softened, without colouring the onion or garlic. Add the (drained) celeriac, potato and stock, bring to the boil turn down to a simmer and cover and cook for around 25 minutes, or until the celeriac is tender.
Once the vegetables are cooked through, add the cream (if using), 1 teaspoon truffle oil and blend to a smooth texture (you can use a stick blender, or put it into a food processor / blender to liquidise it, making sure you don't exceed any maximum liquid guidelines etc.). Add milk / hot water / stock whilst mixing (if possible) until you reach your desired texture (I added 200ml Gold Top full fat milk). Have a taste of the soup, and then add pepper, salt to taste (I added 1 level teaspoon), and the remainder of the thyme leaves (unless the flavour of the thyme is enough for you already) and extra truffle oil to taste, and briefly whizz again to incorporate the thyme leaves in a roughly chopped manner. If you're happy with the seasoning, serve with your choice of garnishes and enjoy!
1. Peel the celeriac and potato and cut into chunks small enough to fit through the lid. To prevent the celeriac from browning, put a little lemon juice into a bowl of cold water, and toss the celeriac in as you go. Peel the garlic and onion, and cut the onion into quarters. Remove the leaves from the stalks of the thyme.
2. Drop the onion and garlic onto running blades, Speed 8. Add the butter (or oil) and onion to the bowl and chop 7 seconds / Speed 4. Scrape down the sides, then cook 5 minutes / Varoma temperature / Reverse Spoon / Speed 1 / MC off.
3. Add the (drained) celeriac and potato to the bowl, and chop 30 seconds / Speed 4 / MC on. (Smaller pieces cook more quickly and evenly).
4. Scrape down, add the stock (you should be below the 2 litre mark) and cook 20 minutes / 100C / Speed 2.5 / MC on.
5. Check the vegetables are tender, then add 100g cream (if using, or add water / stock / nut milk etc.), 1 tsp truffle oil and some pepper, then place the MC on top of the lid and gradually turn the dial up to Speed 10 and blend for 1 minute.
6. Carefully remove the lid, then add the milk (or water / stock / nut milk) until you reach the desired consistency - you could pour it through the lid while stirring on a lower speed. I add 200ml. Make sure you do not exceed the maximum capacity of your bowl.
7. Have a taste of the soup, and then add pepper, salt to taste (I added 1 level teaspoon but maybe only add half at a time if you feel it needs extra), and the remainder of the thyme leaves (unless the flavour of the thyme is enough for you already) and extra truffle oil to taste, and briefly blend again 30 seconds / Speed 10 / MC on to incorporate the thyme leaves. If you're happy with the seasoning, serve with your choice of garnishes and enjoy!
The kids bowls... with homemade rustic spelt and linseed bread. You don't have to be posh, to enjoy posh nosh!