The classic tarte tatin is made, of course, with apples. But the principle of caramelising some delicious, round, sweet things, topping them with puff pastry, then flipping it upside down, works equally well in this savoury interpretation. The shallot/spring onion vinaigrette finishes off the tarte a treat – but, if you fancy ringing the changes, it’s also very good topped with crumbled feta and coarsely chopped parsley.