By Eddie999, member
Posted: February 12th, 2012
Combine the flour, both sugars, salt, and cinnamon or nutmeg, if using, in a medium bowl. Rub in the butter with your fingertips until it's well blended and the mixture crumbles coarsely; it should hold together when you pinch it. Work in the oatmeal with your hands until it's well-distributed. Refrigerate the topping until needed.
Heat the oven to 375 degrees F.
Put the blackberries, blueberries, and raspberries in a large bowl. Taste the fruit and sprinkle on 2 Tbs. to 1/3 cup sugar; for sweet, ripe fruit, use less; for tart fruit, use more.
In a small dish, dissolve the cornstarch in the lemon juice. Pour over the fruit. Add the lemon zest and toss gently.
Pour the fruit mixture into an 8- or 9-inch square (or similar-capacity) glass or ceramic baking dish. Set the pan on a baking sheet to catch overflowing juices. Top the fruit with half of the topping (keep the other half refrigerated) and bake for 20 minutes.
Sprinkle the remaining topping over the crisp and continue baking until the fruit is tender when pierced with a knife, the topping is crisp, and the juices are bubbling, another 15 to 35 minutes, depending on the fruit. Let cool for 20 to 30 minutes. Serve warm.