Preheat a pyrex jug by filling it with boiling water from the kettle. Refill the kettle and boil again
Cover kippers with boiling water then cover with a plate and leave to poach in the jug for 7 minutes
Bring water to a boil and add the white wine vinegar. Give the water a swirl while lowering the heat until barely simmering and then add the eggs to poach for around 3 minutes
Lightly toast the bread and remove the crusts
Drain water and cut kippers in half then let the butter melt from residue heat in the jug
Pour melted butter over kippers and top with a poached egg.