Here on California's Central Coast, the berry farmers in Corralitos grow the most flavorful bush berries. It is worth a special trip in late June to the Farmer's Markets to splurge on a flat of berries (I prefer a mix of the best blackberries, boysenberries, and ollalieberries). If my serving plans don't coincide with the sadly short season, I take them home and lay them out on cookie sheets, unwashed, and freeze them. Then put them in baggies until the worthy occasion to serve them for family and friends. I love to allow the berry flavor to dominate, which makes the humble crumble the ideal platform for these little jewels. —CentralCoastContessa
In advance, make the crumble by mixing the dry ingredients, pulsing in cold butter and egg until the mixture resembles small pebbles. Freeze in a baggie.
Rinse the berries and drain. Allow to macerate for a few hours or all day with the sugar and cornstarch. They should get nice and juicy.
Grease individual baking dishes. Put a little of the crumble mixture into the bottom of each one. Put in the macerated berries. Pour excess juice over. Top with Crumble topping, allowing it to fall naturally into the nooks between berries.
Put the baking dishes on a parchment lined cookie sheet to catch overflows.
Bake at 350 for 45 minutes to an hour. This will depend on your dish size and oven. It's done when the filling is bubbling, and the topping slightly browned.
Allow to cool at room temperature, the flavor gets better with a little time. Serve with honey vanilla bean ice cream or whipped cream.