Place the lemon juice, mustard and egg yolks in a small bowl. Whisk until light. Place over a saucepan of simmering water and whisk as mixture thickens. Gradually add the cubes of butter, whisking all the time until thick. Taste for seasoning. Keep warm either by leaving over the hot water or transferring to a flask.

Bring a large pan of water to the boil. Lower the heat to a gentle simmer and stir to create a whirlpool. Drop the eggs in one by one. Cook for about four minutes then remove with a slotted spoon.

Gently cook the spinach in a little water till just wilted. Drain.

Toast and butter the bread. Place a piece of toast on each plate and divide up the salmon, spinach and eggs. Pour the hollandaise over and finish with a spritz of lemon juice and some black pepper. Serve right away.