To begin with, make the hollandaise sauce. Put the lemon juice and vinegar in a small bowl, add the egg yolks and whisk briskly until light and frothy.
Place the bowl over a pan of simmering water and whisk until thick. Gradually add the cubes of butter, continuously whisking until it thickens further. Remove from the heat, season to taste, and cover to keep warm.
Bring a large, deep frying pan to a rolling boil and gently crack the eggs into the water. Simmer for around 4 minutes, then remove.
While the eggs are cooking, toast the English muffins and butter. Lay slices of the smoked salmon on top of each half, top with the poached egg once cooked, then spoon over the hollandaise sauce. Finish off with some chopped chives, and you are ready to serve.
Notes
Using the same method, try substituting smoked salmon for Dill Gravadlax, for a more flavoursome dish.