Add parsley, oregano, garlic, shallot, serrano pepper, vinegar, salt and pepper to a small bowl stir together. Drizzle in the olive oil while stirring. Taste and adjust seasoning, adding in more salt or vinegar as desired.
1 cup firmly packed fresh flat-leaf parsley leaves, 2 tablespoons fresh oregano leaves, 2 garlic cloves, 1 small shallot, 1 small serrano chili, 2 tablespoons red wine vinegar, 1/2 teaspoon sea salt, 1/8 teaspoon freshly ground black pepper, 1/2 cup extra virgin olive oil