WALNUT CRISP TOPPING:
1. Add 1 cup of walnut pieces to a food processor and pulse until finely ground.
2. In a small bowl, combine ground walnuts, flour, brown sugar, oats, cinnamon. Cut butter into mixture until a coarse crumb forms.
3. Coarsely chop the remaining 1/2 cup of walnut pieces and stir into crumb mixture until incorporated. Set aside while preparing the fruit filling.
APPLE PEAR FRUIT FILLING ASSEMBLY:
1. Preheat oven to 350°F.
2. In a bowl, toss together apples, pears, sugar, cornstarch, cinnamon, salt and lemon juice.
3. Place fruit mixture in the bottom of a 10-inch cast iron pan or baking dish.
4. Sprinkle walnut crisp topping mixture over the top of fruit.
5. Bake for 45 minutes or until fruit mixture is hot and bubbly and topping is golden brown.
6. Serve immediately. Top with ice cream and a drizzle of caramel sauce for extra decadence.