Preheat oven to 350. Place asparagus, sweet potato and garlic on a baking dish. Cover with olive oil and salt and pepper and roast for 20 minutes, until potato is soft. Remove from oven and reserve asparagus tips.
Melt butter in a large pot. Add leek and spring onions. Cook for 5-6 minutes.
Add garlic, sweet potato, and garlic. Stir in broth and curry powder. Bring to a boil, simmer for 5-6 minutes, then puree with immersion blender or transfer to food processor.
Serve with a tablespoon of creme fraiche and the asparagus tips on top.
Recipe by Things I Made Today at https://www.thingsimadetoday.com/2013/06/02/farmers-market-soup/