Prep Time: 60 minutes
Preheat the oven to 400 degrees. Bring a large pot of water to a boil over a high flame. Place the squash cut side up on a baking sheet and rub the flesh with a small amount of oil. Season with salt and pepper.
In a large bowl, toss together the cauliflower and onion with the remaining oil. Season with salt and place on another oiled baking sheet. Place both in the oven and cook until the squash is softened and the cauliflower and onion are tender and slightly browned, turning once, about 30 minutes. Remove from the oven and set aside.
While the squash is baking, boil the potatoes in the large pot with water until soft, about 15 minutes. Remove the potatoes when cooked, leaving the pot of boiling water. Quickly blanch the kale for 3 minutes. Strain, chop and reserve. In a small mixing bowl, whisk together the yogurt with a pinch of salt and pepper. Set aside.Scoop out the squash, leaving 1/2" of flesh surrounding the skin, and place into a large mixing bowl along with the cauliflower and onions. Add the butter and gently mash together, seasoning with a pinch of salt and pepper. Add the kale and stir to combine. Stuff the squash halves with this potato mixture and return to the oven for another 10 minutes until slightly browned. Divide among 2 plates and garnish with the yogurt sauce.