Put the cashews in a bowl and cover completely with water. Soak for about 3 hours and up to overnight.
Drain the cashews, reserving the soaking water, and transfer the nuts to a blender or food processor. Blend until smooth and silky, about 2 minutes.
Scoop the avocado flesh into the blender with the cashews and add the cilantro, olive oil, jalapeno and lime zest and juice and blend until smooth. The mixture should be about the consistency of pancake batter--slightly thick, but pourable. If the mixture is too thick, add some of the reserved water from soaking the cashews. Season with salt and pepper.