400g/14oz chestnut mushrooms, halved
2 garlic cloves, finely chopped
small handful chopped tarragon or parsley
2 red onions, chopped
300ml/10fl oz chicken stock
1 tbsp wholegrain mustard
salt and freshly ground black pepper
1 tbsp olive oil
1 tbsp sweet smoked paprika
1 tbsp tomato pur茅e
1 tbsp butter
250ml/9fl oz soured cream (use reduced fat soured cream if preferred)
3 skinless, boneless chicken breasts, cut into bite-sized pieces