Put the apple pieces into a 2.5 litre (or 2.5 quart) casserole dish and add the remaining apple layer ingredients. Toss the ingredients well until the apples are evenly coated and then press everything down into an even layer.
In a separate bowl, stir together the crumble ingredients until mixed well. They should have a texture similar to wet sand.
Pour the crumble onto the apples and spread it so the apples are evenly coated.
Bake the dish uncovered for 35-40 minutes, until the crumble is golden brown and the apples are soft and bubbly. Remove the dish from the oven and cover it with a lid or foil and let it cool for 5-10 minutes, then serve and enjoy!
Notes
Nutritional values are an estimate and will vary depending on the exact ingredients used and your portion size.
If you want to make this recipe even easier, don't peel the apples.
Store any leftovers in an airtight container in the fridge for up to 7 days.