Cut any large shallots in half. Melt the butter in a 20 cm (8 inch) frying pan with a metal handle if you one. Add the shallots and fry over a medium heat for about five minutes, turning from time to time until just beginning to brown.
Add the honey and vinegar and fry for five minutes more, stirring more frequently towards the end of cooking until the shallots are a deep golden. Add the thyme stems and season well. Leave to cool.
If your frying pan handle is not metal, transfer the shallots to a greased 20 cm (8 inch) shallow round cake tin. Roll out the pastry until a little larger than the diameter of the frying pan or cake tin. Lift over the shallots and tuck down the sides of the pan or tin. Make two small slits for the steam to escape.
Bake in a preheated oven, 200°C / 400° F / Gas Mark 6 for 25-30 minutes until the pastry is well risen. Leave to stand for five minutes, cover the pan or tin with a plate, invert then remove the pan leaving the tarte now on the plate.
Serve warm or cold, cut into wedges with a green salad.
Tips: There’s no pastry to make for this easy upside down tart, simply roll out some readymade puff pastry and then drape over buttery fried shallots glistening with clear honey and dark aged balsamic vinegar.