Place potatoes in a large saucepan and cover with water. Bring to a boil. Reduce heat; cover and cook for 10-15 minutes or until tender. , Meanwhile, in a large skillet, melt butter over medium-high heat. Add onion, celery and poultry seasoning; cook until onion is tender, about 4 minutes. Add kale and ½ cup water from simmering potatoes. Cook until kale is tender and bright green and cooking liquid has reduced by half, about 2 minutes. Add garlic and cook 1 minute; remove from heat. , Drain potatoes, reserving 1/2 cup water; mash with yogurt, salt and pepper. Gently fold in kale mixture and 3/4 cup cheese. Add reserved water, a tablespoon at a time, to achieve a light and airy consistency. Transfer to a serving dish; top with remaining cheese and if desired, additional celery leaves.