In a large skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for about 30 seconds until fragrant, being careful not to burn it.
Add the chicken pieces to the skillet. Season with salt, black pepper, and red pepper flakes (if using). Cook for about 5-7 minutes, stirring occasionally, until the chicken is browned and cooked through.
Add the broccoli florets to the skillet and cook for an additional 3-4 minutes, stirring frequently, until the broccoli is tender but still bright green.
Stir in the fresh spinach and lemon juice. Cook for another 1-2 minutes until the spinach is wilted.
If desired, sprinkle with grated Parmesan cheese before serving.
Notes
For added flavor, marinate the chicken in olive oil, garlic, and lemon juice for 30 minutes before cooking.
Substitute the broccoli and spinach with other vegetables like bell peppers or snap peas for a different taste.