Preheat the waffle maker and preheat the oven to 140C/120C Fan/Gas 1. Put a large wire rack on a baking tray and keep it warm in the oven.
In a large mixing bowl, combine the flour, baking powder, salt and sugar. Whisk in the eggs, milk and butter to combine thoroughly. Mix in the smoked salmon and chives.
Ladle the batter into each well of the waffle maker and close the lid. Cook the waffles for 5 minutes, then lift the lid and check the waffle – it should be golden-brown and crisp. Transfer to the wire rack in the oven and repeat the process with the remaining batter.
For the black pudding, heat a non-stick frying pan and fry the black pudding on both sides for 2-3 minutes.
For the poached egg, bring a large saucepan of water to a simmer. Add the white wine vinegar and swirl the water using a spoon. Carefully break an egg into the centre of the swirl. Cook for 2 minutes, remove and place on kitchen paper. Repeat to cook the remaining eggs.
For the hollandaise sauce, put the egg yolks, lemon juice and a tablespoon water in a blender. Turn on the machine and then slowly pour the warmed butter through the lid. Season with cayenne pepper and salt.
To serve, divide the waffles between four plates and top with the black pudding, spinach, watercress and a poached egg. Pour over some hollandaise sauce and serve.