1. Preheat the oven to 425˚F (220˚C).
2. Make the cauliflower rice: Heat the olive oil in a medium pan over medium heat. Add the scallions and sauté until fragrant, about two minutes. Add the frozen cauliflower rice, season with salt and pepper, and cook until tender and warmed through, about 6 minutes. Remove from the heat and set aside.
3. Make the chicken: Pat the chicken thighs dry and season with olive oil, salt, pepper, and cayenne. In a cast-iron skillet over high heat, sear the chicken thighs, skin-side down, until the skin is crispy, about 10 minutes. Flip the chicken over and transfer the skillet to the oven. Roast for 15 minutes, until the chicken is cooked through.
4. To assemble, divide the cauliflower rice between 2 bowls. Top with the mushrooms, sweet potato, spinach, avocado, and chicken. Store one serving in an airtight container.