In a saucepan saut¨¦ the onion in the margarine for a few minutes until translucent. Add asparagrus, vegetable stock, celery and potato. Cover the saucepan and boil for 15 minutes. Remove from heat and add the fresh tyme.
Blend the asparagus soup until smooth. Put the soup through a fine sieve or strainer to remove the asparagus fibers. Add the soy milk and bring to boiling point. Remove from heat. Add salt and pepper to taste.