Nettle Soup with Mushrooms and Yogurt

Throughout the Balkans, foraged nettles are one of the most sought-after greens. Their deep, sweet flavor differentiates them from other wild leafy greens. On Kea, our garden fills with nettles in the winter and we gather them while still tender, before they suffocate the spinach, kale, chervil, and the other herbs we plant. Wearing gloves, I wash the nettles, discard the thick stems, then blanch the tops in salted water for a few minutes, until just wilted. I drain them but keep the cookin