In a tall glass container, crack the egg; add the salt, garlic, chives, and 2 tbsp. of oil
With an immersion blender, blend ingredients until emulsified, about 20 seconds
Slowly drip in the oil for another 30 seconds or so, until the mayo gets thick and creamy
Alternatively, you can add everything except the 1/2 cup oil, in a blender, and with the motor running, slowly stream in the 1/2 cup of oil until emulsified, about 20-30 seconds