In a large skillet over medium heat, heat the oil until it’s hot, but not smoking. Add the garlic cloves, and fry for about one minute, or until they start to turn golden.
Add the chiles and sunflower seeds, and stir and fry for about 1 to 2 minutes; be careful that the oil doesn’t get too hot, which will cause the chiles to burn and turn bitter (the oil should sizzle but not sputter or smoke).
Remove from heat, add oregano, and let cool for about 10 to 15 minutes, then transfer the skillet’s contents into the jar of a blender.
Add the salt and 2 tablespoons vinegar. Blend until smooth, gradually increasing speed from low to high. Taste, and add more salt and vinegar (you want the tang of the vinegar to balance the richness of the chiles), and a few pinches of brown sugar, if needed, to round out the flavors.
Pour into a jar with a tight-fitting lid, let cool, and refrigerate if not using right away.