Peel roughly 2 sweet apples, cut into small pieces, and set aside half of the pieces. Peel 3 medium onions and finely chop them.
Heat 1 tablespoon rapeseed oil in a large pan over medium-high heat. Sear the chicken breasts for 2 minutes on each side until golden brown. Remove the chicken from the pan and transfer to an oven-safe dish.
Bake at 180°C (350°F) with top and bottom heat for 10-14 minutes until the internal temperature reaches 74°C (165°F).
In the same pan, add the chopped onions and half of the apple pieces. Cook over medium-high heat for 2 to 4 minutes, stirring frequently.
Add 350 ml apple wine, 2 tablespoons vinegar, and 1 tablespoon soy sauce. Season with salt and pepper to taste. Reduce heat to medium and simmer.
After 6 minutes, add the remaining apple pieces and cook for another 5 to 6 minutes until the apples are tender.