Peel and chop the onion. Wash the asparagus, cut off the woody ends. Cut the asparagus into pieces
Heat the fat in a saucepan. Sauté the onion for about 6 minutes. Steam asparagus for the last 3 minutes. Deglaze with stock and milk. Bring to the boil and simmer for about 10 minutes until the asparagus is soft. After about 3 minutes, remove a few asparagus tips for garnishing
Finely puree the soup with a hand blender. Stir in crème fraîche, season soup with salt, pepper, sugar and lemon juice. Arrange the soup and garnish with asparagus