1. Combine the buttermilk, mayo, horseradish, chives and oil in a medium bowl. Season with salt and pepper. 2. Toss the lettuce and apples together and drizzle about 2/3rd of the dressing over this. Toss to coat. Divide between 6 plates. 3. Add the trout to the dressing and toss to coat. Divide the trout between the plates, placing it on top of the mixed salad. Season with salt and pepper and serve.