Soup’s on! There are plenty of myths about homemade soup, including “A soup must be fresh” and “A soup must taste of its ingredients.” These are all false, according to Tamar Adler, author of An Everlasting Meal, who argues that the best soups are authentic—and mature.
The best soups are a day old. Soup mustn’t be fresh, but mature. They needn’t taste of their ingredients, but only give their ingredients somewhere to be left off and picked up again. I learned to make soup from my mother, whose potages contained whatever was around, much of it already cooked: roasted root vegetables, boiled potatoes or turnips, an odd handful of herbs. She served them throughout my childhood, doused with good olive oil and topped with crisp croutons. They were a day old or older. Their ingredients were older yet, and they were delicious.
To make a good, honest, authentic potage, like my mother’s, slice half an onion and a clove of garlic. Cook them, salting as soon as you add them to the pan, with a half teaspoon of fresh thyme in a little butter and olive oil, until tender. If they start to brown, add a few drops of water. Add any combination of roasted squash, root vegetables, and sweet potato and an equal quantity of stock or water.
Let it all simmer for half an hour. Purée in a blender in batches, blending more solids than liquid. If it begins to seem too liquidy at any point, leave some of the broth behind. If it needs more liquid, judiciously add some of what you have left; you can always add more. You can make this days in advance. Warm the soup up slowly in a pot before eating.
If you want a soup of cauliflower or broccoli, begin it the same way, omit the thyme and add a quarter cup of olive oil before blending it and a dab of cold butter once you have. Eat either à la my mother, drizzled with olive oil and topped with crisp croutons.
Or put two cold, peeled roasted sweet potatoes into the bowl of a food processor. Add a few generous spoonfuls of melted butter, a splash of cream, and a quarter teaspoon of smoky paprika. Purée it until it’s completely smooth. Warm it slowly in a pot over low heat, adding a combination of chicken broth and coconut milk until it just seems souplike. Serve squeezed with lime and scattered with chopped cilantro.
For beet soup, do everything just as you do for the squash and root vegetable soup, but serve it cold, drizzled with yogurt, sour cream, or crème fraîche. There is an eye-roll-worthy restaurant chestnut that “today’s soup is tomorrow’s purée.” It is also true. Tomorrow, cook a cubed, peeled potato separately in boiling water, drain it, smash it through a potato ricer or food mill, and mix it into your cold leftover soup. Warm it over low heat in a little pot with a tablespoon of butter. When it’s warm, add a drizzle of cream, call it a purée, and serve.