Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Place the cubed butternut squash and the chicken breast on the baking sheet, then drizzle with olive oil.
Sprinkle the sea salt, black pepper, dried thyme, and cinnamon evenly over the squash and chicken.
Roast for 25-30 minutes until the squash is fork-tender and the chicken reaches an internal temperature of 165°F.
While roasting, sauté the chopped yellow onion and minced garlic in a large pot over medium heat with a splash of water until translucent.
Remove the chicken from the oven and let it rest for 5 minutes before slicing into thin strips.
Transfer the roasted squash into the pot with the onions and pour in the vegetable broth.
Simmer the mixture for 5 minutes, then use an immersion blender to puree the soup until it reaches a velvety smooth consistency.
Ladle the soup into a bowl and top with the sliced roasted chicken breast to serve.