Add all the ingredients to a small saucepan and put over a medium heat, stirring until everything has melted together – about two minutes.
Bring the mixture to a boil, then simmer gently for six to eight minutes.
Blend the sauce with a stick blender, then pass through a sieve and transfer to a jar.
Store in the fridge until ready to use. You can make this up to a week in advance, and it’s all the better for it.