This is the sort of dish that doesn’t really need a recipe, especially once you’ve made it a couple of times.
Avocado Sauce
Avocado Sauce is delicious on all manner of tacos but especially those filled with fish, shrimp, or pork. It is also excellent swirled over gazpacho or any chilled tomato soup. You'll enjoy it with tamales, too.
Directions
Cut the avocado in half, remove the pit, scoop out the flesh and put it into the work bowl (small if you have options) of a food processor or blender.
Quickly chop the serrano and add it to the work bowl, along with the lime or lemon juice. Add several pinches of salt and pulse until very smooth.
Taste, correct for salt and acid and thin with a little water until the sauce is the consistency you prefer. It should not be thick like guacamole but it should not be too thin, either.