Add the cilantro, parsley, garlic, shallots, serrano pepper, and oregano. Pulse until the herbs are chopped finely. Slowly add the red wine vinegar, salt, and olive oil. Pulse to mix.
Chopping by hand
Combine the all of the ingredients in a mixing bowl and stir to combine.
Allow the sauce to rest at room temperature for at least an hour before using to allow the flavors to meld.