Soak the chia seeds in the cold water, refrigerate overnight.
Day 2
Use a blender to combine the soaked chia seeds with the Dijon mustard and vinegar to obtain a sticky, gummy based sauce.
Add the soy milk and blend well.Season with salt and pepper, then pulse to combine.
Pour a thin and steady stream of oil into the centre of the chia seed mixture base. The ‘hole’ in the centre of the sauce will close meaning mayonnaise is ready.
Season to taste and refrigerate overnight before using.