Add the cornstarch, sugar, salt and turmeric to a saucepan.
Add a little of the milk very gradually, stirring as you go to work out any lumps until you have a nice smooth paste.
Gradually add the rest of the milk while stirring.
Place the pan over a medium-low heat and stir gently but constantly, making sure you cover the bottom surface of the entire pan with your stirs. Do not stop stirring or lumps will form.
Keep going until you have a smooth, thick custard. It should take about 10 minutes and will be like a thick sauce or gravy in texture. It should easily coat and cling to the back of a spoon and if you run your finger down the back of the spoon a clear, clean line should remain.
As soon as it reaches that stage turn off the heat, then add the vanilla extract and vegan butter. Stir until the butter is melted and incorporated then your custard is ready to serve.
