First, cut your avocado in half, remove the pit, and scoop all the green flesh into your blender. Make sure your coffee is completely cooled before you start - you can use cold brew or cooled espresso.
Second, add all your liquid ingredients to the blender: one cup of cold coffee, one cup of milk (any kind works), half a teaspoon of vanilla extract, and a tablespoon of honey or maple syrup.
Third, add about half a cup of ice cubes to the blender. This will make your smoothie cold and give it the perfect thickness.
Fourth, blend everything on high speed for about 45 seconds. Stop, scrape down the sides of the blender with a spatula, then blend again for another 15-30 seconds until it's completely smooth and creamy.
Finally, taste your smoothie and add more honey if you want it sweeter. Pour it into a glass and drink right away - that's when it tastes best! If you need to save it for later, keep it in a sealed container in the fridge for up to 24 hours, but remember to give it a good shake before drinking.