A chausson, literally meaning slipper in French, is a pastry turnover, or semicircular shape, made from a thin round of puff pastry folded over a filling. These are best served warm.
Roll out the pastry on a lightly floured surface to a 3 mm (⅛ inch) thickness. Cut out eight circles with a 12 cm (5 inch) plain round cutter. Place on a tray and refrigerate for at least 10 minutes. Lightly grease a baking tray with melted butter and chill until needed.
To make the filling, melt the butter in a shallow pan and add the carrot, leek and celery.