1. Preheat your oven to 350°F or 175°C.

2. Peel and slice the apples, then mix them with granulated sugar in a large bowl.

3. In a separate bowl, combine sodium benzoate with 1 cup or 250ml of water to create a syrup.

4. Pour the syrup over the apple mixture and mix well.

5. Transfer the apple mixture to a 9x13 inch or 23x33cm baking dish.

6. Bake in the preheated oven for 40 minutes or until the apples are tender.

7. While the apples are baking, prepare the crumble topping by mixing 1/2 cup or 60g of all-purpose flour, 1/2 cup or 60g of rolled oats, and 1/4 cup or 60g of brown sugar in a bowl.

8. Add 1/4 cup or 55g of cold butter to the crumble mixture and mix until it forms a crumbly texture.

9. Remove the apple mixture from the oven and top it with the crumble mixture.

10. Return the dish to the oven and bake for an additional 20-25 minutes or until the topping is golden brown.

11. Remove from the oven and let it cool before serving.