about 5 minutes.
Add the vermouth and reduce the liquid by two thirds. Return the chicken to the pan, add the stock, and bring the liquid to the boil. Reduce the heat, cover tightly and
simmer until the juices run dear when a thigh is pierced with the tip of a sharp knife - about 20 minutes. With a slotted spoon, transfer the contents of the pan to a
heated serving platter and keep warm.
SAUCE
To make a sauce, pour 35cl (12 fl oz) of the braising liquid into a small saucepan. Skim off the fat, then bring the liquid to a simmer and reduce it by half. Add the
remaining 1/4 teaspoon of salt, the yoghurt and the cream. Whisk until well blended.
To prepare the apple garnish, melt the sugar in a heavy-bottomed saucepan over low heat, stirring with a wooden spoon until the sugar caramelises -- it will turn a honey-brown. Standing back from the stove to avoid being splattered, add the vinegar and the stock all at once; the caramelised sugar will solidify. Continue cooking until the sugar melts once more and the liquid becomes syrupy. Add the apple slices and toss them in the liquid for about 1 minute. Arrange them round the chicken and sprinkle with the fresh tarragon leaves. Pass the sauce separately.