I love the way a handful of mournfully overripe, positively unprepossessing bananas give rise to this vulgarly triumphant cha-cha-cha of a cheesecake. Well, it is a cheesecake, but the texture is not the usual smooth cream; rather, it is aerated and moussy and as light as its perfume is, contrariwise, compellingly heady. You can make the toffee sauce while the cheesecake is cooking or cooling. Either way, you want the sauce completely cold, but it shouldn't go into the fridge; it will come to no harm sitting out, covered, overnight, or for a couple of days in a cool place. The cheesecake is a different matter: it needs the overnight stay in the fridge and longer won't hurt it. When you make this, do ensure that the cream cheese is at room temperature before you start whisking or processing it. If it starts off cold, it will never — whisk it or blitz it as wildly as you will — cook to the requisite lusciousness. For US cup measures, use the toggle at the top of the ingredients list.