Heat the cream to just below boiling- do not allow to boil.
Whisk egg yolks in a large mixing bowl.
Very, very slowly mix all of the hot cream into the eggs in the mixing bowl (not in the saucepan) to temper the eggs.
Wipe out your sauce pan so it is clean. Pour the custard back into the saucepan. Mix in the sweetener, salt and vanilla extract.
Return the saucepan to the lowest possible heat and continually whisk your custard until it thickens enough to coat the back of a spoon. Note that your custard will continue to thicken as it cools.
Strain custard if you need to and serve.
Brandy Custard- blend in 50-100 ml of brandy once you have made the custard.
Do not boil the cream mix to prevent splitting.Continually whisk your custard to prevent separating and lumps forming. Try to whisk in the corners as this is where the custard will thicken.Ensure your pan is perfectly clean when you pour the custard mix back into it to prevent sticking and lumps forming.If you have lumps in your custard you can strain it.Using too high temperature when whisking your custard in step 5 will result in a separated custard.Halve the recipe to make a smaller amount.If you want your custard to thicken to use in trifles and other recipes, allow it to cool in the fridge. It thickens beautifully as it cools.If your custard separates, simply blitz with a stick blender till smooth.