Heat the oil in a large skillet over medium-high heat until almost smoking. Coat each trout portion well with the blackening seasoning and place the fish into the skillet. Cook for 4 to 5 minutes on each side, or until charred.
For the remoulade, combine the mayonnaise, mustard, paprika, gherkins and parsley in a mixing bowl. Cover with plastic wrap and refrigerate for at least 1 hour.
Transfer to a serving dish and serve with the remoulade.
