Sweet summer stone fruit shines in this simple crumble, which uses crushed cookies and almonds in the topping. Let the kids help; the only special equipment needed is their hands.
Preheat oven to 350 degrees. In a large bowl, use your hands to mash together the almonds, butter, cinnamon, and wafers until well combined but still fairly coarse. Arrange plums in a 9-inch pie dish, and top with almond mixture, pressing it together in handfuls, and then scattering it in large pieces over the top. Bake until plums are tender and juicy and almond mixture is golden, 45 to 50 minutes. (To avoid burning, tent with foil during baking, if needed.) Serve warm or at room temperature.