In a medium-sized sauce pan, heat the olive oil. Add the onions and sauté until they become tender and almost translucent, without colouring. Add the potato and asparagus and stir well. Add the stock and bring to a simmer. Cook for 20 minutes over medium to medium-low heat, until the asparagus are tender.
Puree the soup with a hand blender until completely smooth. Bring the soup back to a simmer and add the cream. Season to taste with salt and pepper and cook for 5 minutes.
Ladle the hot soup into serving bowls and garnish with fresh thyme and edible flowers.