Cover the cashews with water and soak for 2 hours.
Drain the cashews and put into a powerful blender or a food processor. Add 1 1/2 cups cold water, the peanut butter, dates, maple syrup and sea salt. Split the vanilla bean and scrape the seeds into the mixture. Puree until very smooth, thick and creamy (if the mixture becomes too thick to blend, add more water one tablespoon at a time until it's the right consistency).
Make the crust:
Process the walnuts or almonds in a food processor until they look like coarse flour. Add the remaining ingredients and pulse until mixed. Press the crumbs into the bottom of a 9-inch deep pie dish or tart pan with 2-inch sides.
Pour the filling into the crust and place in the freezer for 10 minutes.
Put the chocolate in microwaveable dish and heat on high in 30 second increments, stirring each time, until it's melted. Spoon some of the chocolate in random blobs over the top of the filling (save the rest for serving). Use a skewer or thin knife and swirl the chocolate into spirals (be sure not to touch the crust layer).
Cover the pie and freeze until firm, about 2 hours. Let it thaw at room temperature until it's sliceable. Serve drizzled with more melted chocolate and sprinkled with peanuts.
You need a 9-inch deep-dish pie plate, or a 9-inch tart pan with 2" inch sides (also known as a quiche pan).
Store the pie in the freezer and thaw at room temperature about 15 minutes before serving.