First make your basil pesto (recipe provided by Jennifer Gieseke in this booklet, right after me) and sunflower sour cream (recipe below). Both of these will keep in the fridge for a few days, so you can make them ahead of time.
For the soup; add the leeks, shallots, garlic, celery, bay leaves, some salt and white pepper, and sauté over a low heat for 20 minutes, stirring occasionally. This is no oil sauteing so you may need to add a tablespoon of water every now and then to keep them from sticking to the pan. Take care to not let them turn color, as we wish to keep our soup nice and green. The long sauté time will allow the natural sweetness of the vegetables to come out.
Add the peas and water, bring to a gentle boil and cook for five minutes, just lightly to cook the peas.
Remove from the heat, remove and discard the bay leaves, and use a blender to process the soup as fine as you can.
At this stage you are done if you have a high-speed blender. If not and/or if you wish to have an even creamier and velvety soup, then transfer the soup to a fine sieve, and take your time to pass it through thoroughly - using the back of a ladle to press the mushed-up vegetables through the sieve, rubbing them vigorously on the inside of the sieve. You want to end up with a totally dry pulp in the sieve, which you can then discard.
Transfer the soup to a clean pot and reheat gently. Taste and adjust the seasoning.
To serve, pour the soup into serving bowls and finish with a teaspoon of basil pesto and a teaspoon of sun flower sour cream on top. Alternatively, you can also cut the basil in thin ribbons and sprinkle on your soup (as shown in the photo here).
