Remove and discard about ½ inch of the bottom stem of asparagus (is tough and not edible).
Cut top of asparagus to leave 1-inch tips. Cut remainder of stems into small pieces.
In a large saucepan heat oil on medium low heat.
Add leeks and cook until soft.
Add stock and bring to a boil
Add asparagus stems and cook until tender (about 5 minutes).
Add cleaned spinach and continue to cook for a few minutes.
Remove soup from heat and in small batches puree in a blender and immediately pour into a bowl over an ice bath (to stop discolouration).
Season with salt and white pepper.
Refrigerate for at least 3 hours.
In a pot of salted boiling water blanch asparagus tips, about 3 minutes and immediately plunge into ice bath to stop cooking process.
Place tips on a paper towel to dry.
Finely chop watercress.
In a bowl add crème fraiche and incorporate watercress.
Refrigerate until ready to use.
Pour soup into chilled bowls and top with a small dollop of watercress cream.
Top with asparagus tips and drizzle with a little olive oil.