In a non-stick skillet, heat the olive oil. Add the chicken and cook until golden brown on the outside and no longer pink on the inside. Remove from the skillet onto a paper towel-lined plate.
In the same skillet, add the garlic, onion, celery, and water. Cook until tender.
In a small pot, add the cream and feta cheese and melt to a creamy consistency.
Season the cream sauce with rosemary, lemon zest, nutmeg, and salt/pepper.
Transfer the sauce to the skillet with the vegetables and add the spinach. Stir to combine. Allow to simmer just until the spinach begins to wilt. Turn off the heat.
Serve the cream sauce over the chicken and garnish with chopped parsley.