Trim the tips of the asparagus to 1.5". Cut the remainder of each stalk into 3 or 4 pieces each. Blanch tips in boiling, salted water for 3 minutes, longer if very thick, and cool in ice water. Drain well and set aside.
Cook stalks in boiling, salted water for about 7 minutes until tender. Drain and transfer to a food processor. Purée well. Strain to remove any strings that remain. Combine with chicken stock and salt to taste.
Just before serving, bring soup to serving temperature. In a small, non-teflon coated sauté pan, melt butter over high heat. Brown asparagus tips.
Arrange tips in individual, heated soup bowls. Divide soup among the bowls. Garnish with chervil leaves.