Heat 1 tbsp olive oil in a large skillet over medium-high heat.
Add the chicken, season with salt and black pepper, and cook for 5-7 minutes until golden brown and fully cooked. Remove from the skillet and set aside.
In the same skillet, add the remaining 1 tbsp olive oil and garlic. Sauté for 30 seconds until fragrant.
Add the broccoli and cook for 3-4 minutes until slightly tender.
Toss in the spinach and stir until wilted.
Return the cooked chicken to the skillet and mix well.
Pour in the chicken broth (or water) and red pepper flakes (if using). Let it simmer for 2 minutes to blend the flavors.
Stir in fresh lemon juice for brightness.
Sprinkle with Parmesan cheese, if desired, and serve warm.