Steam cauliflower florets until tender and transfer to a food processor.
Add milk and two teaspoons of light butter spread, pulsing into a smooth, creamy puree.
Meanwhile, heat water in a large sauté pan over medium heat. Add leeks and cook for about 5 minutes, or until tender.
Add garlic and cook another minute. Add kale and toss to coat.
Cover and reduce heat to low, stirring occasionally. Cook for another 10-12 minutes, or until kale is tender. Season with salt and pepper.
Fold cauliflower puree into the kale mixture, until combined.
Transfer to a baking dish and place under the broiler for about 5 minutes, or until lightly browned on top.
Top with remaining buttery spread and serve immediately.
