I love a French tart. As Barry Cryer once said, "if you want an innuendo, I'll give you one", but that is beside the point. I prefer them sweet, but I'm not averse to the occasional savoury one such as tomato and herbs or roast vegetable. The best by far though, is the pisaladière. Sadly, I'm the only anchovy fan in this house which means we never have it. It's not the kind of thing you make in single portions. I have, therefore, made this alternative which uses strong olives and mushroom powder. I find the olives a pretty good substitute and often use them in salsa verde too.The key to this is long and slow. You must take the onions out for a romantic meal, a walk along the Seine, across the Pont Neuf with the lights of Notre Dame twinkling behind you. You must slowly kiss along their arm, whispering sweet nothings by the light of the moon.Then, and only then can you think about the next stage. What's good about this dish is that it is fairly effortless, unless you make your own puff pastry- which I would recommend every once in a while, and yields results that are far greater than the sum of its parts.That is to say, that like the French, you do a little work, then have a long break and sit down to lunch. Whether you have an affair in between is up to you. But the melting, sweet onions and the slightly sharp saltiness of the olives combined with the crisp flakiness of the pastry make this an affair to remember.Ingredients500g white onions, finely slicedSalt to seasonOlive oil320g puff pastryA few sprigs of thymeA pinch of rosemary leaves1tbsp dried mushroom powderA few handfuls of mixed olives, sliced and choppedExcellent olive oil to drizzle (I have a separate special bottle for this purpose)MethodCook the onions in some olive oil in a lidded pan with a pinch of salt, the thyme and rosemary for about an hour on the lowest heat you can. Take the lid of for the final 15 minutes then leave to cool.Heat the oven to 180c.Roll out the pastry on to a lined 32cm baking sheet and trim the pastry to fit. If you've made your own, bravo. It will make a difference. If, however, you feel life is too short or you just couldn't be bothered, never mind. It will still be delicious. (Try and get all butter puff pastry if you buy it.)Prick the base all over with a fork then spread over the onion, leaving a one centimetre gap around the edge. Brush the edge with beaten egg.Spread the onion all over, dust with the mushroom powder then dot with the olives. Cook for about 15-18 minutes until the pastry is golden. This is best served warm, not hot, so leave to cool for about 20 minutes. A tomato salad with the hint of shallot and some crusty baguette is perfect with this.