Lightly dust a work surface with the flour, then roll out the puff pastry until it is slightly longer than the salmon and 3 times the width.
Lay the salmon in the middle of the pastry and brush it with the olive oil, sprinkle over the rosemary and season with salt and pepper. Diagonally cut the pastry from the salmon to the edge of the pastry in 2cm slices on both sides. Brush the pastry with the egg wash, then fold over the slices from left to right to form a lattice. Trim off the pastry from either end of the salmon, then brush with the egg wash
Place the salmon on a buttered non stick baking tray, then place in the oven on the middle shelf and cook for 25 minutes, or until golden. Once cooked remove from the oven and leave to cool slightly.
While you are waiting for the salmon to cook, bring a medium sized pan of salted water to the boil, then cook the broad beans and runner beans for 2 minutes, drain and refresh under cold water, then squeeze the broad beans out of their shells.
To make the remoulade, mix together the mayonnaise and Dijon mustard in a medium sized bowl, add the celeriac, broad and runner beans, season and mix well.
Once the salmon is cooked serve warm with the remoulade.