Buttery, sweet braised leeks meet a bright, mildly-tart dill-yogurt sauce. Great as a light vegetarian lunch or a side dish for broiled fish and meats. Pairing inspired by Diana Henry, Braising technique from many sources, Sauce adapted from Yotam Ottolenghi
Trim roots and dark green tops off of leeks, leaving the root end intact so the leeks don't fall apart when sliced. (Dark green tops can either be discarded or saved for making stock.) Discard any tough outer layers. Slice leeks in half lengthwise and rinse well to remove grit from between the layers. Dry and set aside.
In a large sauté pan or stove-safe gratin dish, heat butter and olive oil over medium heat until foaming subsides. Add leeks in a single layer, cut side down, and cook until lightly browned, about 3 minutes.** Turn leeks, discarding any papery layers that dislodge, and brown the second side, 2-3 minutes.
Add wine to the pan, scraping up any browned bits, and simmer for 2 minutes. Add enough broth to come about halfway up the sides of the leeks. Cover with a lid or foil, reduce heat, and gently simmer for about 20 minutes, until leeks are tender when pierced with the tip of a knife. Leeks should be soft, but not mushy.
Transfer leeks to a platter with a slotted spatula, draining braising liquid. Sprinkle with a pinch or two of salt, some freshly-ground pepper, and let cool. Leeks are best served slightly warm or at room temperature.
Make the Sauce and Serve
In a small bowl, whisk together Greek yogurt, sour cream, olive oil, lemon juice, kosher salt, garlic, parsley, and dill. Season to taste with additional salt. Refrigerate until ready to serve.***
When ready to serve, spoon a dollop of Dill Sauce atop each leek and sprinkle with ground Sumac and additional freshly-ground pepper.
<p>*Brands of Greek yogurt vary in tartness. Start with 1-1/2 teaspoons of lemon juice and adjust to taste. I use either full-fat or 2% yogurt here, which is usually milder in flavor.</p><p>**Jumbo leeks might not fit in your pan in a single layer. In this case, brown the leeks in two batches, adding additional butter and olive oil to the pan between batches as needed. Return all leeks to the pan before deglazing with the wine; it's okay if they overlap while braising.</p><p>***Since braised leeks have a decent moisture content, I like to serve the sauce on the thicker side. If you prefer a thinner sauce, add a little milk or buttermilk to taste.</p>
<p>Leftover braised leeks make a delicious Leek Soup! Just place the leeks in a blender or food processor (I use my Vitamix) with a little chicken or vegetable broth. Blend until the soup reaches your desired consistency, adding additional broth as needed. Heat, season with salt and pepper to taste, and serve with a dollop of dill sauce.</p>