This is, justifiably, one of the most popular of the herb butters. Blanch 2 ounces (50 grams) fresh tarragon leaves for 1 minute in boiling salted water. Refresh the leaves and dry them on a towel. Grind the blanched leaves with a mortar and pestle or in a food processor. Combine the tarragon paste with 8 ounces (250 grams) butter.