Place sliced apples in a 8x8 square baking dish, sprinkle with half of cinnamon and place in oven for about 10 minutes while preparing topping.
For the topping, mix the other half of the cinnamon with the brown sugar, the ground and chopped nuts and the crushed graham crackers. Add the oil and mix with your hands.
Remove apples from oven and sprinkle topping to cover the whole pan. Place back in oven for about 30 minutes until browned and crispy on top.
Serve with vanilla ice cream or whipped cream if desired.