This is not a soup so much as the first fifteen minutes of any soup you will ever make. Sweated aromatics, cut small and cooked slowly in good oil until they are soft and sweet and have given up their water. Make a double batch on a Sunday and you are twenty minutes from lentil soup, chicken soup, or a chowder on any weeknight.

Gather your mince as you go. Working through celery, onion, and leek in sequence leaves a board covered in scraps, and a crowded board is where knife accidents and uneven cuts come from. Scrape each vegetable into its bowl before you start the next one, and keep the whites of the leek separate from the greens.

The whites need a head start. Leek and scallion whites are dense and take twice as long to soften as the greens, so they go in first and the greens go in at the end — otherwise you get scorched green bits floating over aromatics that are still raw in the middle.