In a heavy pan, combine 1 litre (35 fl oz/4 cups) non-dairy milk with 80 g (2¾ oz) caster (superfine) sugar and a pinch of fine sea salt flakes. Very gently simmer, stirring frequently, until reduced to about 350 ml (12 fl oz). This could take 1 hour. Stir in 1 teaspoon vanilla extract.