5 spring onions (aka welsh onions) with large white bulbs about the size of a golf ball (not green onions/scallions with their tiny bulbs)
2 garlic cloves, minced
1 medium potato, diced very finely
2 lbs asparagus
1 small bunch Italian parsley, tied up with kitchen twine
8 c water or chicken stock
1/2 C sour cream
1/2 C whole milk or evaporated milk
juice of 1 small lemon
salt and pepper to taste
Salted boiling water, for blanching
ice water bath
Sauté the onion, garlic and potato until softened. Prepare the asparagus by snapping off the woody ends and reserving for the stock. Meanwhile, bring a large pot of well-salted water to a boil and blanch the top part (non-woody) of the asparagus spears for 3-4 minutes, afterwards plunging immediately into an ice water bath to halt cooking.
Add water or broth to the soup pot as well as the woody asparagus ends and the twined-up parsley. Bring to a boil and then reduce to a simmer. Cook on low for about 45 minutes. The liquid should have reduced by about 1/3. Remove the woody asparagus ends and parsley and discard. Add in blanched spears which have been cut into small pieces. Cook until the asparagus is softened and then remove the soup from the heat. Allow to cool for about 5 minutes at which point purée in a blender in batches, adding the sour cream to one of the batches. Add all the soup back into the pot along with the evaporated milk, lemon juice, and salt and pepper to taste, and keep warm on the lowest setting, being careful not to let it boil or get too hot lest the acid in the lemon juice curdle the cream/milk. If desired, you may also pass the puréed soup through a sieve before returning to the pot and adding the lemon juice, in order to filter out any bits of asparagus stem, onion or potato skin that didn’t blend.
Serve alongside buttered freshly baked bread.