1 Begin by adding a little olive oil to a large saucepan on a medium heat. Add the garlic and onion, frying gently for about five minutes so they soften while being careful not to burn the garlic or it will taste bitter.
2 Next, tip in the spices along with the celeriac and parsnip, stirring everything together so they get a nice coating.
3 Pour in the vegetable stock and allow the mixture to cook through for about 15 minutes – the aim is for the vegetables to be completely soft, so keep going if they’re not. Then, add the milk.
4 Turn down the heat and season with salt and pepper. Taste to check the temperature has cooled (and to adjust your seasoning if need be), and empty the soup into a blender, ready to blitz. Whizz it for about 30 seconds to get your desired consistency – we like this soup smooth and velvety.
5 At this stage, you can chill your soup until it’s ready for heating and serving. You could even freeze it to enjoy at a later date – simply defrost, and reheat thoroughly. Whenever you choose to enjoy it (we’ll be having it on Christmas Day for sure), you can make your croutons as it warms through.
6 Heat your oven to 180ºC fan or gas mark six, chopping up the sourdough into little nuggets as you wait. Now, drizzle a baking tray with olive oil, scattering the croutons across it before adding a dash more oil over the top along with salt and pepper so that every crouton gets seasoned. Bake for 15 minutes – or until crispy.
7 For serving, ladle fresh-from-the-stove soup into a bowl with a drizzle of olive oil in the middle of each one and at least four or five croutons per person – the more, the merrier.