Soak the cashews overnight (or for at least 6-8 hours) in the water.
In a blender or food processor (will have more texture in a food processor), add the drained cashews, salt, oil, nutritional yeast, and a few cracks of pepper. Add in a tablespoon or two of water. Blend.
Add another tablespoon of water after a minute of blending. Continue to blend and add a little water until the mixture reaches a cream-cheese like consistency. Careful not to add too much water at a time.
Spread the vegan cheese onto each baguette slice.
Slice a large section of the apple. Slice that into fine semi-circles, very thinly (almost transparent). Take three of these at a time, fan them out, and place on top of the crostini.
Garnish with a small slice of spring onion, and a pinch of hemp hearts. If not vegan, consider adding a drizzle of honey for presentation (but it really doesn't need it!)