I learned the secret to making the best, crunchiest fruit crumble over two decades ago. And I subsequently ignored it. A pastry chef friend shared the technique. Instead of sprinkling the raw crumbs on top of the fruit, where they absorb the juices and turn a little mushy on their undersides, he spread them out in a pan and baked them separately, until crisp and cookielike. When fruit and topping finally meet, the crumbs are much better able to hold their own.