Add all the ingredients to a sauce pan without heating. Whisk until it is lump free from the corn starch. Place saucepan over medium heat and cook for 10-15 minutes while stirring. Taste test and add any extra vanilla, salt, etc. if needed to taste.
The mixture is ready when you lift your whisk and it leaves little ‘ribbons’ of custard. You will see the custard start to thicken.
Remove saucepan from the stove and cool for 10 minutes while stirring occasionally. If it is lumpy, blend with immersion blender.
When the custard has thickened further, pour into your tart base. Chill for at least 4 hours in the fridge or 2 hours in the freezer. Decorate and serve!