1 Avocado = 8oz
Wash avocado. Slice down the middle, lengthwise, working around the pit. Twist each half of the avocado until it pulls apart. Use a spoon to pry out the pit, or stick the blade of a sharp knife into the pit and twist until the pit pops out. Cut slices lengthwise in the avocado just down to the skin and then peel the skin back. Or, scoop the flesh out of the avocado with a spoon.
Puree in a food processor or blender until smooth. Add water / breastmilk as needed to reach desired consistency.
Try to use all of the puree at once since avocadoes don't refrigerate or freeze very well. If you must refrigerate leftovers, seal them in an airtight container.