Technical Stages :

• Add the white mushrooms and chervil and tarragon bunch to the clear brown veal stock.
• Dissolve the potato flour or cornstarch in a bowl with the white wine or Madera.
• Pour gradually the cornstarch on the boiling stock, whisking, to bind it as you want.
• Let boil and reduce over moderate heat, frequently skimming, for an hour.
• Filter through a chinois.
• Cool down quickly and keep refrigerated for 48 hours maximum.