In a small, lidded saucepan, bring the water to a gentle boil with the cashews, Brazil nuts and pecans. Simmer for 10 minutes, until the nuts have softened.
Transfer the nuts and liquid to a food processor and add the remaining ingredients. To use the vanilla pod, split it in two lengthwise then scrape each side with the back of a knife to remove the seeds (use the seeds and discard the pod).
Process until completely smooth and creamy. This may take 5 minutes or so, depending on your food processor. You will need to scrape down the sides intermittently to ensure everything gets incorporated.
Serve immediately, drizzled with a touch more maple syrup.