Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Toss the cubed butternut squash, chopped apple, diced onion, and minced garlic with olive oil, sea salt, black pepper, and cinnamon.
Spread the mixture in a single layer on the baking sheet and roast for 25-30 minutes until the squash is fork-tender and slightly caramelized.
While the vegetables roast, poach the chicken breast in simmering water for 12-15 minutes until cooked through, then shred it finely with two forks.
Transfer the roasted vegetable and apple mixture into a high-speed blender, add the vegetable broth, and blend until the texture is completely velvety.
Pour the soup into a bowl, fold in the shredded chicken, and top with a swirl of Greek yogurt before serving.