Mix the chia seeds, almond milk, key lime zest, maple syrup, and vanilla extract together in a bowl. Whisk for 30 seconds until everything is well combined.
Place in the fridge and allow to firm up for 2 hours or overnight.
Add the cashews to a blender or food processor with the coconut milk, maple syrup, lime juice, lime zest, and matcha powder. Blend until completely smooth. (You may need to scrape down the sides a few times as you blend.)
Spoon the chia pudding evenly into 4 little jars. Pour the lime mousse mixture on top of the chia pudding.
Place in the fridge and let set for 2 hours before eating.