Melt butter in a large pan over a medium high heat and gently sauté the apples with a sprinkling of sugar until they begin to colour, about 5-7 minutes. Set aside in a bowl.
In the same pan, heat the olive oil. Brown the chicken fillets on both sides until golden.
Add the onion and garlic and cook for a further five minutes.
Pour in the brandy and cook for a few minutes before adding the chicken stock.
Turn the heat down to medium low, loosely cover the pan with a lid and simmer gently for 25-30 minutes.