In a small bowl, stir together the sour cream, chives and lemon juice. Season with salt and white pepper. Cover and refrigerate until needed to blend the flavors.

Heat the olive oil and butter in a soup pot over medium heat. Add the asparagus and onion; cook and stir until onion is soft, about 5 minutes. Add the garlic and thyme, and cook just until fragrant, about 1 minute. Stir in the flour until smooth, then gradually whisk in the chicken stock to avoid causing lumps. Add the potatoes and bring to a simmer. Simmer over medium heat until potatoes are tender, about 20 minutes.

Puree the soup in a food processor or blender, or use a stick blender in the pot. Return to the pot and bring to a gentle simmer. Season with salt and white pepper.

To serve, ladle soup into warmed bowls and garnish with a dollop of the chive sour cream and a few chunks of crabmeat. Garnish with additional chives if you have extra.