Makes enough for one 1.75-quart dish and one 1-quart dish.  
Adapt this recipe to suit changing seasons/ingredient availability. Apple cranberry would be a nice combination. Why not use some pears? Or lemon? Combinations of fresh or frozen blueberries, raspberries and blackberries are delicious. 
To freeze the crumble: Under-bake it during the initial bake so the fruit is still quite firm (when you reheat it later, the fruit will continue to cook). Allow to cool. Tightly cover the crumble with foil and a lid and place in the freezer for up to 2 months. Bake, covered with the foil, in a pre-heated 375 degree F oven for 40-60 minutes until heated through. 

For the topping 
-4 Tbs. butter
-About 3 Tbs. old-fashioned oats
-About 3 Tbs. all-purpose flour
-About 3 Tbs. walnuts, roughly chopped
-1-2 Tbs. sugar
-Pinch of salt
-1/2 tsp. almond extract (optional) 
For the filling 
-About 3 pounds granny smith apples, peeled and cut into thick slices
-1 ½ to 2 C. fresh or frozen raspberries
-1 to 1 ½ Tbs. minute tapioca (or 1 Tb. flour) 
-Sugar to taste
-Pinch of salt
-Preheat oven to 375 degrees F. 
-Grease baking dishes. 
-In a medium-sized bowl, combine the topping ingredients using clean hands. Press tablespoon-sized amounts of dough between your fingers to create clumps. 
-Adjust butter/flour ratio as necessary to achieve the consistency of a dry, crumbly cookie dough. Adjust sugar to taste. Set aside. 
-In a large bowl, combine the filling ingredients. 
-Spread the fruit filling evenly into baking dishes. 
-Sprinkle the topping over the fruit. 
-Bake until the fruit is bubbly, and the top is golden brown, about 40-60 minutes. You can also test the firmness of the apples by spearing with a fork or skewer. The apples should be tender but still have some resistance. 
-Serve hot or warm with vanilla ice cream.