Add the egg, lemon juice, mustard, and salt to your food processor. Process for about 10-20 seconds, until it is creamy.

Now we're going to add the oil. Start the food processor and pour the oil in a very slow, steady stream. This is the most important part when making mayo. After all the oil has been incorporated, stop the food processor.

Use a spatula to mix in the sliced chives. Store in the refrigerator in an airtight container until ready to use.