The recipe calls for Chervil, a herb similar to parsley. I didn't have either, so actually used some fresh sage, which was lovely! I prepared this sauce to accompany Recipe#328329, by chef#925731. This sauce recipe comes from the "Pasta Cookbook", published by Merehurst Press, original title, "Nudeln".
From Zaars Kitchen Dictionary:
CHERVIL: The leaves and root of this parsley family herb are edible and have a mild anise flavor. The leaves are a curly and dark green. Chervil is one of the main ingredients in Fines Herbes.
Season: available year-round
How to store: Chervil does not dry well, so it is best when used fresh.
How to prepare: Use like parsley, though most flavor is lost when boiled.
Matches well with: asparagus, carrots, cheese, chicken, eggs, fish, peas, potatoes, salads, sauces, soups, spinach, tomatoes, veal, venison
Substitutions: parsley or tarragon