Whisk the gram flour with water in a saucepan, and leave it to stand for 20-30 minutes for the flour to hydrate.
On medium heat, bring the mixture to a boil and keep whisking until it thickens and turns into a thick paste. The texture will be very similar to custard. You’ll have to taste it to make sure that the gram flour is cooked out before removing it from the heat.
Once it’s cooked, remove from the heat and let it cool to room temperature. Then place in the fridge until the mixture is cold. It will have a rubbery feel to it.
Place in a food processor, or a high-speed blender. Then blend on high with lemon juice and mustard.
Add salt, vinegar, sunflower oil and blend until it’s creamy and smooth.
Mix in olive oil, and have a taste and see if you would like to add more salt or acidity.
Store in glass jars in the fridge for up to 3 weeks.