Place the salt into the Thermomix bowl and mix on Speed 10 for 5 seconds.
Scrape down the sides of the bowl.
Add the water and cream of tartar and cook for 5 minutes, 60 degrees, Speed 3.
Leave to cool for 5 minutes.
Add the plain flour and the oil and mix together for 50 seconds, Speed 4.
Knead for 1 minute on Interval Speed.
Check the texture and if it's a little sticky, add some more flour and knead for a further 30 seconds.
Separate the playdough into several bowls.
Add 1 tiny drop of food colouring (and a sprinkle of glitter - optional) to each bowl and mix together with your hands until the colour is evenly dispersed (wear gloves!).
Wrap the playdough in cling wrap and store in an airtight container in the fridge.