1. Remove the skin and pit from the avocado, slice into small pieces (~ 1/2" cubes), and freeze. Keep these in the freezer until frozen. This gives the shake the right temperature and texture without watering down the taste with ice.
2. Put the frozen avocado, rice milk, and sugar in a blender and blend until it reaches the desired consistency. You may have to mess around with the amount of sweetener, but a tablespoon of sugar usually does it for me.
My research adviser is from the Philippines and told me about how they would make avocado shakes with milk, so I decided to try it with non-dairy milk!
I've tried this with soy milk, and it isn't nearly as good.
Source of recipe: Inspired by a recipe from my teacher and veganized.