Pulse cauliflower in a food processor until fine and roughly the shape of rice. Set aside.
Heat olive oil in a skillet or large non-stick pan to medium-high heat. Add garlic and cook 1-2 minutes until lightly browned.
Add chicken to pan and sprinkle with thyme, salt and pepper. Cook 7-10 minutes,
rotating halfway, until browned and cooked through. Remove chicken from
pan and cover to keep warm.
Add chicken stock to pan and scrape bottom with a wooden spatula to
loosen browned bits.
Reduce heat to medium and stir in cauliflower rice and green onions. Cover and
cook 5-7 minutes, or until slightly tender.
Stir in spinach leaves, lemon juice and zest. Cook 2 minutes more until spinach is wilted.
Divide mixture into bowls and top with cooked chicken breast.