Preheat the oven to 450 degrees F. Combine all of the dry ingredients, seasonings, and herbs. Brush each trout fillet with the softened butter. Sprinkle the buttered side of each trout fillet with the pecan crust and press firmly with your hand to completely cover each fillet.
Brush a cookie sheet with the remaining butter. Place the un-breaded side of the trout down on the buttered cookie sheet. Bake for 10 to 12 minutes or until the flesh is firm and flaky.
To make the watercress salad and apple cider vinaigrette:
In a large bowl, toss the lettuce, the apple slices, and the grated horseradish root. In a separate bowl, combine the cider vinegar, lemon juice, minced shallot, ground fennel seed, salt and pepper. Then whisk in the apple cider, olive oil, and walnut oil. Dress salad with the vinaigrette.
Using a large spatula, carefully lift the trout onto a plate. Spoon the horseradish cream over the crusted trout. Serve with a watercress salad with apple cider vinaigrette.
To make the horseradish cream: Chill the reduced heavy cream until cold and thick. Combine all ingredients and gently mix. Keep cold until it goes on warm fish to keep from breaking.