Bring a large pot of salted water to a boil and cook the pasta until al dente. Drain and set aside.
Season the chicken pieces with lemon pepper and a pinch of salt.
Heat olive oil in a large skillet over medium-high heat. Add the chicken and cook for 5–7 minutes until golden and fully cooked. Remove and set aside.
In the same pan, melt butter and sauté the leek, garlic, and green onions for about 3 minutes until softened.
Add chicken broth, lemon juice, lemon zest, and Dijon mustard. Stir and simmer for 1 minute, scraping up any browned bits.
Add spinach and cook until just wilted.
Return the chicken to the pan and pour in the cream. Let it simmer gently for 2–3 minutes.
Add the cooked pasta and fresh herbs, tossing everything together to coat evenly.
Stir in parmesan cheese and adjust seasoning if needed.
Serve hot, garnished with extra herbs, lemon zest, or cheese.