Preheat oven to 180 C / Gas 4. Lightly grease a 23cm springform tin. Stir together crushed biscuits and brown sugar in a small bowl, then drizzle with coconut oil and stir. Add just enough milk to make crumbs stick together. Press very firmly into bottom of tin. Bake 10 minutes. Keep oven on.
Meanwhile, blend cheesecake-batter ingredients in a blender until completely smooth and no bits of cashew remain, giving blender a rest every minute or so and scraping down sides with a rubber spatula. The cheesecake filling should be completely smooth and not grainy: This takes about 1 minute with a high-powered blender or about 5 minutes with a standard blender.
Lightly grease the inside of springform tin above baked base. Pour in cheesecake filling and jiggle to spread evenly over the base. Bake until top is lightly puffed and edges are golden, 45 to 50 minutes.
Cool to room temperature on a rack, about 1 hour. Chill, covered, at least 3 hours or, even better, overnight.
Slice cake with a thin, sharp knife dipped in water. Dollop each slice with vegan whipped cream, dust with cinnamon and sprinkle with crystallised ginger.