Raw Fine Herb Butter

A compound butter of the classic French kind, worked soft rather than melted, and finished with acid and heat from lemon and cayenne. Ranhofer gives no quantities, so the balance is yours to set.

• Working quantityHalf a pound of butter to roughly half a cup of finely chopped mixed herbs, a teaspoon of lemon juice, salt to taste and cayenne on the point of a knife. That yields enough to finish eight to ten portions of grilled fish or steak.
• "Pimpernel" means salad burnetIn nineteenth-century kitchen French, pimprenelle is Sanguisorba minor, salad burnet, a cucumber-scented leaf once common in gardens. It is not scarlet pimpernel (Anagallis arvensis), which is not a food plant. If burnet is unavailable, a little cucumber-fresh borage leaf or simply more chervil covers the gap.
• "A warm basin" is not a hot oneThe bowl should be barely above room temperature, enough to bring cold butter to a soft, plastic state. If the butter breaks to oil the emulsion is gone and the herbs will sink through it.
• Wipe, do not wash, the butterThe instruction to wipe fresh butter in a cloth is about removing surface buttermilk and moisture, which sours quickly and shortens keeping. A modern unsalted butter needs only to be blotted if it looks damp.
• Dry the herbs thoroughlyWater clinging to washed leaves will bead out of the finished butter and make it weep. Spin or towel them dry before chopping, and chop with a sharp knife rather than a processor, which bruises tarragon and chervil into a grey paste.
• Chervil and tarragon lastBoth lose their anise scent fast once cut. Chop them at the moment of mixing; parsley, chives and watercress can be done a little ahead.
• Cayenne is a background noteThis is seasoning, not a chilli butter. Start with a pinch, mix, and taste after the butter has sat five minutes, since heat and salt both read stronger once the fat has firmed.
• Shaping and keepingRoll in parchment into a cylinder and chill, then cut coins to melt over grilled meat, fish or vegetables. Refrigerated it keeps about five days before the herbs darken; frozen, about two months.