Preheat the oven to 200 °C or 180 °C for a fan assisted oven.
Arrange the apples and pears in an 18 x 30cm ovenproof dish creating a deep layer of fruit.
Sprinkle over the ground spices and salt and drizzle with the maple syrup. Use your hands to rub the seasonings all over the fruit until well coated. Transfer to the oven to bake for 12 minutes to soften the fruit.
Whilst the fruit cooks, you can prepare the crumble topping. Add the ground almonds, cinnamon, salt and buckwheat flour to a mixing bowl. Crumble in the flaked almonds and stir well to combine.
Add the maple syrup and stir into the topping.
Add the coconut oil and use your fingers to rub the mixture together to form a thick crumble consistency.
Remove the part cooked fruit from the oven and gently stir. Reduce the oven temperature to 180°C or 160°C for fan assisted.
Scatter the crumble topping in an even layer across the fruit. Return to the oven for a further 15 minutes until crisp and golden.
Whilst the crumble cooks you can prepare the custard. Add 3/4 of the almond milk to a small saucepan and bring to a gentle boil.
In a small bowl, whisk the arrowroot powder together with the remaining almond milk to form a smooth paste.
Reduce the almond milk to a simmer and add the maple syrup, vanilla and salt.
Add the arrowroot paste and whisk continuously until well combined.
As soon as the custard begins to thicken, remove from the heat. This will thicken further on standing so remove from the heat just before it reaches your desired consistency. Serve hot over the crumble.