Slice each chicken breast in half lengthways so you have 4 thinner fillets. Season both sides with salt only. No pepper here as the sauce brings plenty.
Heat some cooking oil in a large frying pan over a medium-high heat. Add the chicken and cook for 2–3 minutes each side until golden. Remove to a plate and leave to rest.
In the same pan, add the onion and cook until it softens.
Add in the garlic, and the crushed peppercorns and cook for 30 more seconds, then carefully pour in the brandy. Let it simmer for 20–30 seconds so the alcohol cooks off, scraping up all the sticky bits from the bottom of the pan.
Turn the heat on high. Add the beef stock and simmer hard for 4 minutes until reduced by about half.
Stir in the cream. Reduce the heat to medium-high and simmer for 3–4 minutes until the sauce thickens and lightly coats the back of a spoon.
Return the chicken and any resting juices to the pan. Simmer for 2–3 minutes, spooning the sauce over the top, until the chicken is cooked through and the sauce has thickened slightly more. If it gets too thick, loosen with a splash of water or cream.
Stir through the chopped chives and taste for seasoning. Serve straight away.