There are few things more versatile or more satisfying than Potage Parmentier (Leek and Potato Soup) or one of its myriad variations. It’s good freshly-made and better the next day. Hot or cold, it makes a lovely start to dinner; served with some left-over meat, a great lunch. It's a great mid-afternoon pick-me-up, either straight out of the 'fridge or zapped in the microwave.
As delicious as is basic leek-and-potato soup, we often include other vegetables or herbs: broccoli stems, asparagus stalks, a large handful of parsley or cress (pretty much whatever is available): the variations are endless. This is one of the classic ways the French utilize left-over or less-than-perfect vegetables bought cheap from the market - a principle of both taste and economy that all would do well to adopt.
You shouldn't be a stickler about using leeks, either: while they have a more subtle flavor than onions, they can be expensive and/or difficult to source out of season. Feel free to use regular onions (the milder yellow/Spanish varieties are best) or use a couple of bunches of scallions (spring onions).
The only rub comes when it’s time to puree the soup. While it can be pureed in a blender, it’s much better to use a food mill. Blenders tend to make the potato starches glue-like and pulverize the woody parts of the other vegetables. The food mill doesn’t change the texture of the potato starch and strains out the vegetable pulp. It takes a little extra muscle, but it’s well worth the effort.
Using the chopping blade in a food processor (Cuisinart) will also puree the soup without the potato separating provided the action is pulsed and not overdone, however the mixture should be sieved if woody-cored root vegetables such as turnips or parsnips are used. Some recipes suggest using a potato ricer (masher) which may work quite as well, since the potato and the leeks are very soft; and the result is a nicely textured soup.
This recipe makes two quarts of soup, though it's worthwhile to double or triple it; left-overs easily last 7-10 days in the refrigerator, though you’ll probably eat them long before that time.
- 3 - 4 cups sliced leeks or onions (about 1 lb. or 450g)
- 3 - 4 cups (700-900g/2lb) floury potatoes (eg. Idaho, Maris Piper), peeled and thickly sliced
- 2 quarts (2 litres) water. A proportion of light chicken or vegetable stock made be used.
- 2 tbs. salt or 1 tbs. sea/rock salt
- White pepper (ideally - for color) to taste. Use fresh-ground black pepper otherwise.
- 4 - 6 Tbs. heavy (double) cream
- 1 - 2 cups (up to 450g/1lb) vegetables (optional)
- 1 - 2 handfuls flat-leaf parsley or watercress (optional)
- Peel and thinly slice the potatoes and onions. If using leeks, remove the roots and dark green leaves; wash twice as long as you think necessary to remove the grit. Thinly slice any optional vegetables or roughly chop any optional herbs.
- Place the vegetables, water and salt in a pot and bring to a boil; Lower the heat and gently simmer (partially covered) for 45—50 minutes. The soup is done when you can easily mash the vegetables against the side of the pot.
- Puree the soup using a food mill fitted with the fine disc. Optionally, “pulse” it in a blender until just smooth and pass through a fine sieve.
- Chill the soup if it is to be served cold or gently reheat it to a simmer. Refrigerate any left-overs. It will keep for days if refrigerated in a covered container as soon as it cools.
- Add 1½—2 tsp. cream (or whole milk) per portion just before serving. You’ll need more cream if you’re serving the soup hot or if it’s a bit watery; the idea is to create a smooth, silky puree, but you don’t want the taste or mouth feel of the cream to predominate. Taste and adjust for salt and pepper.
- Snipped chives are the classic garniture for leek-and-potato soup. When we include asparagus, we use steamed asparagus tips as a garnish; with broccoli, use steamed broccoli flowerets—you get the idea. Of course, if you’re just pouring a mid-afternoon mug for yourself, who cares how it looks?
- After cooking the soup, leave it to cool in the refrigerator for one to two hours. It will taste better when heated up to serve!
- Raw vegetables should be added to the soup at the beginning of the cooking time; if using left-over vegetables or herbs, add them after the soup has been cooking for 30—40 minutes, so they cook just long enough to completely warm through.
- If using "regular" table salt instead of kosher salt, reduce the amount of salt to 1-1½ tbs. A chilled soup usually requires slightly more seasoning than that added to a hot serving; this can be added individually to taste.
- A combination of young buttery parsnips and a couple of punnets of mustard-and-cress makes the classic French Puree Pasternak. A teaspoon of potato, rice or corn starch should be used to stabilise the puree which should be milled or sieved.