Bring a large pot of water to a boil and add salt until it tastes like the sea. Fill a bowl with ice and cold water and place it near the stove. Line a strainer with cheesecloth (double layer if it’s not very fine) and set over a bowl.
Blanch chives and herbs in boiling water 10-15 seconds. Using a fine-meshed spider, immediately transfer to ice water. Once herbs are cold, spread on a clean kitchen towel, roll up, and press gently to dry.
Run a knife through herbs to chop them a little, then purée in a blender with preserved lemon, oil, and salt, stopping before blender heats up as this can turn your oil brown.
Pour oil through prepared strainer. Stir a little to help it along, but don’t press on solids or oil will be cloudy.
Make ahead: Up to 1 week, chilled airtight; bring to room temperature and stir or swirl before using.
Makes 1 Cup