Put the sliced cucumber into a bowl, sprinkle with a tablespoon of rock salt and leave for 30 minutes to draw out the juices.
After thirty minutes place the cucumbers in a colander. Squeeze out and discard all the juices and place the cucumbers in a clean bowl.
Pour approximately four tablespoons of vinegar into a small saucepan. Add the sugar and the tea bag. Gently heat the mixture and allow the sugar to dissolve. Squeeze and remove the tea bag after 45 seconds.
Allow the mixture to cool.
Once cooled, pour onto the cucumber and stir. Set aside to infuse.
For the Hollandaise Sauce:
Melt the butter slowly in a pan over a low heat, stirring occasionally. Remove from the heat and pour into a jug.
Place the vinegar, shallot, peppercorns and bay leaf in a small saucepan over a high heat and bring to the boil. Cook for 1-2 minutes, or until the liquid has reduced to approximately one and half tablespoons.
Fill a medium saucepan one third with water and bring to the boil, then reduce the heat until the water simmers. Put the egg yolks in a heatproof bowl and place over the simmering water. Pour the vinegar from the pan through a sieve into the bowl with the eggs. Whisk until pale, thickened and glossy.
Gradually add the warm melted butter in a steady stream, whisking constantly until the sauce is smooth, thick and shiny. Add a pinch of salt and the juice of half a lemon and whisk again. To avoid the sauce from splitting you may need to lift the bowl off the heat every now and then.
Leave to one side while you cook the sea trout.
For the Steamed Sea Trout:
Place a steamer rack in a saucepan over approximately 3/4inch of simmering water. Place the fish in the steamer, skin side up and steam for 6 minutes. This will leave the very middle of the fish slightly raw, avoiding overcooking. By the time you have plated up it will have cooked through and be perfect.
Take 4 or 5 mint leaves and roll into a cigar shape, slice them finely.
Drain the cucumber, squeezing the liquid out as before. Add the mint and mix through.
Spoon the cucumber on to the serving plates.
Remove the trout from the steamer and gently pull off the skin.
Place the trout on top of the cucumber and season with a pinch of sea salt and some white pepper.
Add a large dollop of hollandaise on top of the fish and serve immediately.