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Vinegar, Basil
Fill a wide-mouthed bottle with fresh green basil-leaves, cover them with vinegar or wine, and let them steep for ten days. If a very strong essence be required, the liquor must be strained off, and more leaves be added to it, to steep in it for another fortnight; when this is done it must be corked down. When used, a table-spoonful will give to mock-turtle soup the basil flavour.
A straightforward cold infusion that still works exactly as written. A few points on vessels, timing and the vinegar itself.
- The vinegar to useWhite wine vinegar or cider vinegar keeps the basil flavour clean; malt vinegar will bury it. The "or wine" alternative gives a much shorter-lived product, since wine lacks the acidity that preserves the infusion — treat a wine version as something to use within a week or two, refrigerated.
- Pack the leaves, don't bruise themFill the jar loosely with dry leaves and press them just enough to submerge. Bruised leaves tend to give a grassy, muddy flavour rather than the clove-and-anise note of basil.
- Everything must stay under the surfaceLeaves floating above the vinegar will darken and can go mouldy. Weight them down with a small glass disc or top up with more vinegar as they settle.
- Ten days, and no advantage in longerThe infusion is essentially finished in a week to ten days at room temperature, out of direct light. The second steeping with fresh leaves, as the recipe says, is the way to strengthen it — extra time on spent leaves does nothing.
- Vessels and closuresUse glass, and a plastic-lined or cork closure. Vinegar corrodes bare metal caps, which will taint the batch and eventually leak. Sterilise the bottle before the final corking.
- Which basilSweet or Genovese basil is the default. Thai basil gives a stronger aniseed character and holy basil a peppery one; both work but will not taste like the original.
- Yield and keepingA jar filled with leaves and then covered yields noticeably less strained vinegar than the jar's nominal volume, since the leaves take up much of the space. Strained and corked, it keeps well for many months in a cool dark cupboard, though the colour fades from green to a straw brown within weeks — that is normal and not a fault.
- Beyond mock turtleA tablespoon works equally well in a tomato salad dressing, a bean soup, or for deglazing a pan for chicken. Add it off the heat; boiling drives off the volatile oils that were the point of making it.
Herb vinegars were the Victorian kitchen's answer to a problem refrigeration later solved: how to keep the taste of a summer herb available in February, and books of the period carry a whole run of them alongside this one. Basil earns its place chiefly as a soup seasoning, and the reference to mock-turtle soup is the giveaway. That dish, made from a boiled calf's head in imitation of the genuine turtle soup of civic banquets, was often seasoned with basil, so a bottle of the essence would have answered when fresh leaves were out of season. The technique itself is far older than the book: steeping aromatics in vinegar or wine runs back through medieval and Roman cookery, where the acid served as both extractant and preservative long before anyone described it in those terms.