In a large bowl mix together sweetened condensed milk and 2 tablespoons chicken stock powder. Place chicken breasts in bowl and turn to coat all sides of the chicken. Cover and refrigerate for at least 5 to 6 hours; overnight is best.
Preheat oven to 220 degrees C.
In a roasting dish heat 4 tablespoons of the oil on the stove top over medium-high heat. Cook onion, carrot, celery, chillies, garlic and shallot with rosemary, thyme, bay leaves, juniper berries, peppercorns, cloves and cinnamon stick in oil until vegetables are evenly browned. Stir in 1 cup wine then cover and cook in the preheated oven for 25 minutes; gradually add remaining wine to the dish during this time. Stir in chicken stock and continue cooking for 1 hour.
Strain contents of roasting dish into a saucepan. Cook over medium-low heat to reduce sauce. Melt chocolate in the sauce stirring until smooth.
In a large frypan heat the remaining two tablespoons of oil. Season chicken with remaining chicken stock powder covering both sides generously. Cook in hot oil until evenly browned and cooked through. Pour sauce over chicken and heat through.