Cut off the roots from the leeks and then also the green part. Keep the green leek for a green leek coulis. Now make an incision to the middle of the leek and wash it well under running cold water. Then cut it in even thick rings. Now transfer the leek into a preserving jar and press it down a bit. Then submerge the leek completely with water. After weigh the jar. An empty jar weighs 600 grams and now it weights 1600 grams, so the water and leek weigh 1000 grams. Then add 1.5% salt. So, in this case 15 grams. Press it down once more. Now close the lid and gently mix it to dissolve the salt. Then open it up and remove the sealing ring. If you don’t do this, it might explode. Label it and then let it ferment for 6 or 7 days. Every other day I pressed it down and tasted it until I was happy with the flavor. I fermented mine for 7 days. Once it’s fermented drain the water and keep it for the sauce. Then transfer the leek into a pan and cover it with the cream. Now bring this to a boil and then let it simmer for 15 minutes. I only add the cream for some fattiness, for me it doesn’t need any other flavor. The leek is already delicious! Then transfer it into a blender and blend it till smooth. Once it smooth add a touch of xanthan gum and blend it for another minute. This will prevent the cream from splitting. Then keep it in your fridge for later.