In a large bowl, mix together the coconut milk, apple cider, maple syrup, cinnamon, nutmeg, ginger, and salt.
Stir in the chia seeds. Whisk the mixture every couple minutes for 10 minutes, then refrigerate. It will start to thicken right away, but it's best to refrigerate it for a couple hours so it has a chance to fully thicken.
To serve, divide the chia pudding into 4 bowls and top with diced apples and walnuts.