We wanted to make crumble a traditional dessert in our own little family and this is a great way to get kids to try different fruits. You could keep this as just plums or even add some cherries or pear. The plums really do have so much flavour just on their on though with a few apples. The secret to making a really good plum crumble is choosing good plums. They need to be in season and ripe. That's why this recipe is so simple, because when you use ripe plums, that flavour is really all you need.