A sure sign of summer in a Southern kitchen is a bowl or window ledge full of vine-ripened tomatoes from the garden. But an even surer one in mine is a jug of cold soup in the refrigerator. From early June (May when we lived in Savannah) until well into September, there's at least one such jug or bowl of a soup that's as good cold as warm. Though it can be heated to warm us on the odd cool evening, it's mainly there to have cold, to soothe and stir heat-blunted appetites.
At the moment, there are actually two: this summer's first batch of vegetable soup (still not quite like my grandmother's, but getting there) and a summer squash puree with leeks and thyme.
I don't really follow a recipe anymore. It's the same basic formula as leek and potato soup, with whatever vegetable I want/need to use up substituted for most, or all, of the potatoes. The seasonings are simple and there's no broth—which, if it's going to be worth it, has to be homemade and ends up being a lot more work and for nothing, because in this, even a really good broth just gets in the way of the other flavors.
Cold Summer Squash Soup with Leeks and Thyme
Yellow summer squash have a natural sweetness to them that they lose the longer they're separated from their vine, so if your squash isn't as fresh as you'd like, add a light teaspoon or so of sugar—not enough to make it sweet, but just enough to bring back that natural sweetness.
This is also lovely with green zucchini, though the flavor and color is of course very different.
Don't add the milk and cream until you're ready to serve it: it'll keep much longer.
Makes 8 servings as a soup course
2 pounds yellow summer squash such as crooknecks, patty-pan, or yellow zucchini
2 large leeks
3 tablespoons unsalted butter
1 medium yellow onion, trimmed, split lengthwise, peeled, and thinly sliced
Salt
A small handful (about 4-5 large) fresh thyme sprigs
Whole white pepper in a mill
2 cups cold whole milk
1 cup cold heavy cream, plus more for serving
2 tablespoons fresh thyme leaves, for garnish
1. Wash the squash well under cold running water, gently scrubbing to remove any grit that may be clinging to them. Pat dry, trim away the blossom and stem ends, and slice them crosswise about ¼-inch thick or cut them into roughly equal chunks. Trim the root end of the leeks, split them lengthwise, and rinse under cold running water, root end up, folding back the layers to remove the dirt between them. Pat dry and thinly slice the white and inner pale greens.
2. Put the butter, onion, and leek in a large, heavy-bottomed saucepan over medium-low heat. Lightly sprinkle with salt, cover, and gently sweat until the leeks and onion are soft and have thrown off most of their liquid, about 10-12 minutes. Check and stir it regularly: the moisture shouldn't completely evaporate and the vegetables should not be allowed to brown at all.
3. Add the squash and thyme sprigs, a generous pinch of salt, and enough water to just cover them. Raise the heat to medium-high, bring to a boil, then reduce the heat to low, loosely cover, and simmer until the squash are tender, about 20 minutes. Turn off the heat and season with several liberal grindings of white pepper. Let it cool somewhat then remove and discard the thyme stems. Most of their leaves will have fallen off.
4. Puree the soup in batches in a blender or food processor. Pour it into a covered storage container, let it cool completely, uncovered, then cover and refrigerate until well-chilled, at least 2 hours but preferably 4-6. The soup can be made up to 4 days ahead to this point.
5. When you are ready serve it, stir in the milk and cup of cream, taste and adjust the salt and pepper, and let it sit at room temperature for 10 minutes before ladling it into soup plates or cream soup cups. Drizzle each serving with a little cream, sprinkle on a few thyme leaves, and, if liked, a light grinding of white pepper.