The charm of this simple dessert is obvious: It takes sweet summer fruits and cooks them down so that everything good about them becomes even better.
For filling
1 1/2 pounds purple plums, cut into 1/2-inch wedges
1 cup blueberries (5 ounces)
1 cup blackberries (5 ounces)
1/3 to 1/2 cup packed light brown sugar (depending on sweetness of fruit)
For topping
1 cup rolled oats
1/4 cup all-purpose flour
1/3 cup packed light brown sugar
1/2 stick unsalted butter, cut into bits and softened
1/4 teaspoon salt
Preheat oven to 425°F with rack in upper third.
Toss together all filling ingredients in a 2-quart shallow baking dish and bake 10 minutes.
Meanwhile, blend together all topping ingredients in a bowl with your fingertips until butter is evenly distributed and mixture is crumbly.
Stir fruit filling, then sprinkle oat mixture over it and bake until topping is crisp and golden and fruit is bubbling, about 30 minutes.
Makes 4 servings
