Pre-heat the oven to 160C/325F/Gas Mark 3. Place the butter in a food processor with the garlic, herbs and seasoning. Blend briefly and transfer to a small bowl with a spatula. Chill until needed.
Heat a flameproof casserole dish over a medium-high heat. Add the oil, then add the chicken breasts, skin-side down. Cook for a few minutes on each side until golden brown. Transfer to a plate.
Add the leek, carrot, celery and thyme to the casserole and sauté for about 5 minutes until just starting to soften but not colour. Pour in the wine and chicken stock and allow to bubble down a little, then arrange the chicken breasts on top. Cover with a lid and bake for another 20 minutes, or until the chicken is tender.
Transfer the chicken breasts to a warm plate. Whisk two-thirds of the herby garlic butter into the vegetable mixture and spoon onto warmed plates. Arrange the chicken breasts on top and place a scoop of the remaining butter on each one. Add the mash and serve at once.
- 75 g (3 oz) unsalted butter, at room temperature
- 2 garlic cloves, crushed
- 2 tablespoons chopped mixed herbs (flat-leaf parsley, tarragon and basil)
- 1 tablespoon olive oil
- 4 corn-fed chicken breast fillets (skin on)
- 1 small leek, cleaned and finely chopped
- 1 carrot, peeled and diced
- 2 celery sticks, diced
- the leaves from 3 sprigs of thyme
- 4 tablespoons dry white wine
- 2 tablespoons chicken stock
- salt and freshly ground black pepper
- mashed potatoes, to serve