Sprinkle the insides of the fish with the salt, pepper and sugar mixture (everything!). Finely chop the dill and place on one of the two halves. Put the second half on top and wrap tightly in aluminum foil. Place in an elongated vessel and weigh down with a board and weights. Put in the fridge for 3 - 4 days (turn every day).
Then remove most of the dill and cut the trout open like gravlax.
Serve with the appropriate gravlax mustard sauce (can be bought ready-made). Delicious, tasty - much finer in taste than salmon.