Trim the roots and dry ends off the leeks. Halve them, rinse and thinly slice them. Peel and finely chop the onion. Peel and grate or crush the garlic.

Warm a large pan on a medium heat for 1 min, then drizzle in ½ tbsp olive oil. Add the leeks, onion and garlic and fry for 10 mins on a low medium heat, stirring often, till the leeks have started to soften.

Meanwhile, peel and chop the potato into small cubes. Fill and boil the kettle.

When the veg have cooked for 10 mins, scoop about a quarter of the leeks out into a bowl. Cover with a plate and set to one side. Add the potato to the pan and stir. Add a good pinch of salt and pepper and pour in 900ml hot water from the kettle. Bring the soup up to a bubble then pop on a lid and simmer for 10 mins.

While the soup simmers, finely chop the parsley stalks and roughly chop the leaves, keeping them separate. Place a small frying pan on a medium heat and add the walnut halves. Toast them for 2-3 mins till fragrant and slightly darkened. Tip onto a board and when cool, finely chop them.

When the soup has cooked for 10 mins, take the pan off the heat. Add the parsley stalks. Using a stick blender, blend the soup till is smooth. Add a splash more water if you want a thinner consistency. Stir in the reserved leeks and pour in half the pot of cream. Taste and add more salt or pepper if you think it needs it.

Ladle the soup into warmed bowls. Top with the chopped parsley leaves and walnuts. Drizzle 1 tsp thyme oil over each bowl and serve.