Andouilles or andouillettes are French pork sausages, sold ready-cooked. They can sometimes be bought in a good butchers or really good-quality markets with a meat counter. This recipe can also be made with ordinary pork sausages. If the sorrel is too strong for you, you can use half sorrel and half spinach. Or, if you cannot acquire any sorrel at all, use spinach and sharpen it with either some lemon juice or a touch of tamarind water.