Instructions

Bring 2 quarts water to boil in medium saucepan. Fill large bowl halfway with ice water and set aside. Add 33 grams parsley leaves and tender stems and 33 grams cilantro leaves and tender stems to boiling water and cook until bright green and wilted, about 20 seconds. Immediately shock herbs in ice bath using tongs or spider skimmer. Once herbs are cooled, transfer to kitchen towel and squeeze between hands to wring out excess moisture (herbs should be as dry as possible).
Process herbs and 167 grams neutral oil in blender on high speed for 2 minutes. Strain oil mixture through fine-mesh strainer set over bowl; set aside to strain for 20 minutes.
While oil is straining, combine 100 grams serrano chiles, halved lengthwise and sliced thin crosswise; 100 grams garlic cloves, peeled; 33 grams raw pepitas; 1 tablespoon raw sunflower seeds; and remaining 167 grams oil in clean, dry saucepan. Bring to simmer over medium-high heat, then reduce heat to medium-low and cook, stirring frequently, until garlic is golden brown and tender, 15 to 20 minutes. Transfer oil mixture to bowl and let sit until cooled to room temperature, about 20 minutes. (To speed it up, put oil mixture in bowl over ice bath, stirring occasionally.)
Transfer cooled chile-garlic mixture to blender and process on low speed until coarsely chopped, about 10 seconds. Transfer to bowl and stir in strained herb oil, 1 tablespoon cider vinegar, 1½ teaspoons kosher salt, 1 teaspoon sugar, and 1 teaspoon dried Mexican oregano. You can serve this right away but flavors will continue to develop as mixture sits. If time allows, let sit in refrigerator for 12 hours then bring to room temperature and season with salt, sugar, and/or vinegar to taste before serving. (You can refrigerate salsa for up to 1 week; be sure to bring it to room temperature and taste for seasoning again before serving.)