Slice the leek/onion/shallots thinly. Fry slowly on a low-medium heat for 5 minutes in a large saucepan, don’t let them burn.
Chop the potato into small pieces and add them and the broth to the pan. Simmer for 12-15 minutes, until the potato is soft.
Finally, add the coconut milk or yogurt or cream, rocket/arugula, mustard, pepper, nutmeg and half the salt. Give it all a good blend with a hand blender. You can make it completely smooth, or leave a few lumps for texture.
If you would like croutons, slice the bread into squares and fry in olive oil on a medium heat for 2-3 minutes. Add some pressed/crushed garlic and fry for another thirty seconds. Done!
When serving, garnish with a little hazelnuts. Add croutons if using. Done!
Adapted from original recipe: : https://hurrythefoodup.com/rocket-soup/