The abundance of fresh ripe berries is one of the pleasures of summer. Each variety in the seasonal trinity-blackberries, blueberries and raspberries-works beautifully in this recipe. Remember to treat fresh berries gently after purchase. If not using them immediately, store them for up to 2 days in the refrigerator. Rinse the berries briefly in a colander before use, then pick over the berries and discard any that are moldy or mushy. Let dry in the colander or on a layer of paper towels.