Combine 2 cups (500 milliliters) of concentrated white stock with 1 bunch of tarragon and bring the mixture to a simmer. Reduce if necessary until it is lightly syrupy. Turn off the heat and cover the pan. Let the tarragon infuse in the stock for 10 minutes. Strain the sauce and finish it with 4 ounces (125 grams) of Tarragon Butter and 5 ounces (150 grams) of plain butter. Adjust the seasonings.