Preheat oven to 350 degrees F.
Toss the apples with the sugar, cinnamon, and cornstarch until well coated. Place in a 9 by 12-inch baking dish.
Put the flour, brown sugar, and butter in a food processor, and pulse until crumbly. Add the nuts and pulse, to coarsely chop them. Place the topping onto the apples and bake for 40 minutes. Remove from the oven and serve warm.
Recipe courtesy of La Campagne, Cherry Hill, NJ