In a jar or a glass container combine almond milk, maple syrup, cacao powder and chia seeds. Stir until chia seeds are covered with the almond milk. Cover with a tight lid and place in the refrigerator for at least 4 hours or overnight.
Use a chef's knife to cut the mango in half. Place 1/2 mango, almond milk and maple syrup in a blender, and blend till smooth. Pour the mixture in a jar or a glass container. Stir in chia seeds. Cut the remaining mango into small cubes and stir into the mixture (OPTIONAL: leave some mango cubes for garnishing). Cover with a tight lid and place in the refrigerator for at least 4 hours or overnight. Pudding will be ready when the chia seeds have plumped up.