My mom is a magnificent cook, and this blueberry cake has been a favorite for many generations of people around the world. It is very forgiving, freezes very well, and can easily be doubled for a 9"x13" pan. While fresh blueberries are best, I stock up on them when in season, freeze them, and then bake this cake with frozen berries, and it is still wonderful. One issue in our family, though, is that some of us (who shall remain nameless) annoy others by picking off all the crumbles from the top, thereby diminishing the experience for everyone else. What can I say? It's hard to resist!