On a Friday afternoon in March, Petra Sloane bought three and a half pounds of beef marrow and knuckle bones from her butcher on Broughton Street in Edinburgh and carried them home in the rain in a paper bag that gave out at the corner of Howe Street.
She roasted the bones in a 425-degree oven for forty minutes, which is the only fast step in a project that would otherwise take twenty-four hours.
While the bones roasted she chopped two carrots, two onions, two ribs of celery, a small head of garlic split crosswise, and a leek she had been meaning to use for a week.
The bones came out the colour of dark mahogany. She slid them, along with their rendered fat, into a fifteen-quart stockpot she inherited from a retired hotel chef in Pitlochry in 2018.
She added the vegetables, a tablespoon of tomato paste, a small handful of dried mushrooms, two bay leaves, ten peppercorns, and cold water to two inches above the bones.
The pot went on the back left burner of her stove at four in the afternoon. She brought it to a bare simmer, skimmed the grey foam from the top for the first twenty minutes, and then she left it alone.
Sloane does not subscribe to the school of stockmaking that requires constant attention. A well-skimmed pot at a true bare simmer, she has found, does not need supervision. It needs time.
The pot stayed at that simmer all Friday night and through the small hours of Saturday morning, the surface trembling, the kitchen warm, the windows running with condensation.
She topped up the water once before bed, once when she came down at six on Saturday morning for coffee, and once at noon. Otherwise she left it.
By six in the evening on Saturday, the broth had reduced by almost half. It was the colour of strong tea and smelled like a butcher's shop in a building that had been a butcher's shop for a hundred years.
She lifted the bones out with tongs, strained the stock through a fine-mesh sieve lined with damp cheesecloth, and let it cool in the pot on the back step for two hours.
She refrigerated the strained stock overnight. By Sunday morning a half-inch cap of yellow fat had set on the top, and the stock beneath it had set into a firm amber jelly that held the shape of a fork tine pressed into it.
The fork-tine test is the one Sloane uses. If the jelly holds the print of a fork, the stock has the body she wants. If it slumps, she returns the strained stock to the pot and reduces it further.
This batch held the print. She skimmed off the fat, saved it in a small glass jar for roasting potatoes, and divided the jelly into ice-cube trays and one-cup containers.
The yield was just under a quart of true demi-glace consistency and three quarts of regular stock. The whole thing cost her about nine pounds in bones and an evening of low-grade kitchen warmth she would have wanted anyway.
The stock cubes went into the freezer drawer, where they would last her two months. She dropped a single cube into a pan when she wanted to deglaze. She used three cubes to start a risotto. She made an onion soup with eight of them on a cold Tuesday in April.
The marrow she scooped from the roasted bones before they went into the pot, salted, and ate on toast at five o'clock with a glass of cold beer, before the long simmer had really begun.
She is asked, sometimes, whether the twenty-four hours is necessary. She has tried this stock at twelve hours, eighteen, twenty-four, and thirty-six. Twelve is good. Eighteen is better. Twenty-four is what she settled on. Thirty-six was, she found, a marginal improvement that was not worth the bother.
What twenty-four hours buys you, over twelve, is depth and body. The collagen has more time to break down. The water has more time to take on flavour. The fat, separated and saved, is more useful.
Sloane does not buy commercial stock. She has not in eleven years. The freezer stash is replenished about every two months, and the project has become one of the steadiest rhythms of her domestic life.
The pot goes on the back burner. The kitchen gets warm. Friday becomes Saturday. The stock becomes the thing that quietly improves every braise, every risotto, every pan sauce for the next eight weeks.
She is not evangelical about it. She mentions it when people ask. Mostly she keeps the stock in the freezer and lets it do its work.
