Preheat the oven to 200°C fan bake. Take butter out of fridge so that it can soften slightly.
Place the pears, lemon juice, cinnamon, nutmeg, honey and water in a saucepan over low to medium heat. Cover and cook, stirring occasionally, for 5 minutes or until the pears have softened slightly. Add in the mandarins and combine ingredients, cooking for a further 2 minutes. Transfer mixture to a square oven dish.
Gently pulse the oats, pumpkin seeds, desiccated coconut in a blender or food processor for 5-10 seconds so that they are course and crumbly. Transfer to a large mixing bowl.
Add in cinnamon, coconut sugar and combine ingredients. Cut the butter into small pieces and rub it into the topping mixture so that it becomes crumbly. You will know the topping is ready when it resembles coarse crumbs, with a few pea-sized clumps of butter within.
Top the pear mandarin mixture with the crumble topping.