The Tarbais bean is a 'culinary gem' and has two notable plus points for the gourmet:  an exceptionally fine and delicate skin which gives an exceptional creamy tenderness, and a pleasant, sweet and long lasting flavour, rare for a bean.  Its cultivation is complex.  Produced by hand by individual growers, the extra precision and delicate handling in harvesting and sorting considerably extends the production time.  But it's worth it:  on the plate, the Tarbais bean has no competition and greatly enhances meats of quality.  Its origins remain unknown.  For a long time it was thought to have been imported from the Americas, though certain experts are saying that this variety comes from China.  We still have a lot to learn about it."