Melt the butter in a sauté pan over medium heat. Add onions and cook until soft – 5 minutes. Mix Medjool dates, breadcrumbs, nuts, herbs and onion together.
Using a sharp, non-serrated knife, cut a pocket into the thickest part of each chicken breast – being careful not to cut through. Leave approx ½ inch on all sides.
Fill pockets with Medjool date mixture, season with salt and pepper and brush both sides with a little olive oil. Place in a shallow baking dish and pour in the wine.
Bake 30 – 35 minutes until chicken is fully cooked.
