Place a large jug onto mixing bowl lid and weigh 600 g grapeseed oil into it, then set aside. Break 4 eggs into another bowl and set aside.
Add 2 tsp salt, 2 Tbsp raw sugar and 65g apple cider vinegar into mixing bowl and cook 3 min 30 sec/100°C/speed 1.
Set machine to 45 sec/speed 3.5, adding eggs through hole in mixing bowl lid. Add 3 Tbsp Dijon mustard, or to taste and mix a further 15 sec/sp 2.
Insert MC and with Thermomix set to 3 min/speed 6, very slowly pour the oil onto mixing bowl lid, allowing it to drizzle in and emulsify.
Scrape down lid and bowl.
Scoop into clean jars or squirty bottles.