I first learned to make these smoothies in high school back in Austin. Aside from California, Texas is home to the largest Vietnamese population in the States. I learned more about the history behind this in an Asian Studies class in college. Basically, following the Vietnam War, the Vietnamese immigrants were siphoned through resettlement agencies whose goal was to "minimize the impact on local communities." So, they scattered the new immigrants throughout the States to godforsakenly cold areas. This didn't stop them from gravitating to more sensible climates. Ergo, Texas.
My brother used to eat avocados straight out of the skin with a spoon (maybe he still does). He calls it "green butter;" the Vietnamese call it "butter fruit." Being from Texas, I know avocados to be used to savory preparations like guacamole. My mind screamed in protest when I learned of avocados being used in smoothies. Whatevs. You just have to try it.
The traditional Vietnamese recipe calls for avocados, milk, sugar and condensed milk. I added in a few flavor enhancers (lemon zest and mint) to brighten up and enhance the avocado flavor. The result was what I'm sure Jesus sips on every day perched atop a pearly gate.
(makes 1 large smoothie)
1/2 ripe avocado*
3 tablespoons condensed milk
2 tablespoons sugar
2 fresh mint leaves
1 pinch of lemon zest
1 tumbler of ice (about 8 ice cubes)
2/3 cup milk
*If the avocado yields to firm, gentle pressure, you know it's ripe.
It's important to put the ingredients into the blender in order of the ingredient list. The reason being the avocado and condensed milk help lubricate the blades. Also, the more "intense" ingredients need to be nearer to the blade to be shredded up evenly then dispersed throughout the smoothie. The milk goes in last because if you put it in first, the ice won't be as near the blade and it needs to be in order for the ice to be ground up quickly without melting too much.
The best technique for blending this smoothie is pulsing. Pulse in short staccato-like increments until the ice is evenly broken up with no large chunks. Then you can crank it up to full speed to blend evenly. The resulting texture should be very thick - so thick you'll have to eat it with a spoon. If you like a thinner smoothie, use less ice. I, personally, dig on the thick texture. It's more of a dessert than a drink.
I realize it is below freezing outside as I'm typing this. I eat/drink smoothies when I want. You should too.