Lightly coat a 2-1/2- to 3-quart (13x9-inch) baking dish with nonstick cooking spray and wipe with a paper towel to spread evenly; set aside.
For topping: In a large bowl, whisk together the 3/4 cup brown sugar, flour, the 1-1/2 teaspoons ginger, the 1 teaspoon cinnamon and salt. Using a pastry blender, cut in butter until the mixture resembles coarse crumbs. Stir in walnuts and pecans; set aside.
In a very large bowl, whisk together the 1/2 cup brown sugar, cornstarch, the 3/4 teaspoon ginger and the 1/2 teaspoon cinnamon. Add apples slices. Gently toss until coated.
Transfer apple mixture to prepared dish. Sprinkle topping over the apples. Cover the dish with foil.
Bake in a 375 degree F oven for 30 minutes. Remove the foil and bake for 25 to 30 minutes more or until top is browned and apples are tender. Let cool for 20 to 30 minutes before serving. If you like, serve with ice cream or whipped cream. Makes 8 servings.