1. Bring the water with the vinegar to a boil in a high pot.
2. Preheat the oven to 200 °C.
3. Place the rosti burger in the oven for 12 min
4. Melt the butter in a saucepan. Prepare the butter by scooping off the foam and remaining only the transparent part.
5. Split the eggs and put the egg yolks in a second saucepan.
6. Beat the egg yolks with the water. Put the pot on the heat and beat with a whisk frothy like sabayon. Remove the pot from the heat before the eggs solidify.
7. Whisk the clarified butter with the sauce.
8. Season the Hollandaise with a pinch of salt, cayenne pepper, sharp mustard and the juice of a quarter lemon.
9. Using a whisk, make a vortex in the large pot of water and vinegar.
10. tip The water to boil the eggs may taste a little like vinegar but not be overly acidic. The vinegar ensures that the clotting of the eggs is faster.
11. Break each egg into a separate bowl and slide them into the water one by one.
12. Poach the eggs for about 3 minutes. Scoop the eggs out of the water with a skid.
13. Drain on a clean kitchen towel.

Finishing and serving

1. Remove the rosti from the oven and drain on kitchen paper.
2. Place the rosti in the middle of a plate and top with the smoked salmon finish with a poached egg, a large spoonful of Hollandaise sauce.