In a sauce pan, melt the butter and mix in the flour. Cook out for 1-2 minutes - gradually add the milk and continue to cook for a further 6-8 minutes.
Finally add the Orkney cheddar and egg yolk.
Remove from the heat and set aside.
In preparation, preheat the oven to 200°C and butter the soufflé dish well and set aside for later.
Place the egg white in your mixing bowl and whisk until peaks are formed.
Place half the whites on top of the cheesy base, add the herbs and smoked salmon and mix - now add the remaining whisked egg whites and stir, making sure to not over stir.
Decant the mixture into the buttered soufflé dish - flatten the top usinga palette knife and put into the oven for 18-20 minutes then serve hot.