400g/14oz chestnut mushrooms
2 garlic cloves, crushed
1 unwaxed lemon, finely grated zest and juice
4 banana shallots, finely chopped
small handful fresh tarragon, leaves picked, roughly chopped, plus extra for garnish
1 tbsp Dijon mustard
100ml/3½fl oz chicken stock
300g/10½oz fettucine or tagliatelle
1 tbsp olive oil
150²µ/5½´Ç³ú crème fraîche
6 skinless, boneless chicken thighs, cut into 3cm/1in pieces
100²µ/3½´Ç³ú pancetta or bacon lardons