In a medium bowl, whisk together the yogurt, lemon juice, honey, mustard, salt, and pepper until smooth. In a small skillet, heat poppy seeds on medium heat. Cook, shaking the pan occasionally until seeds are fragrant and begin to pop, about 2-3 minutes. Immediately stir into the dressing.
Place greens in a large mixing bowl. Slowly pour some of the dressing over the greens. Gently mix to coat the greens with the dressing. Add more if necessary until all greens are lightly coated. Be careful not to overdress the salad. Serve immediately.