1. Heat the butter in a sauté pan and add the sliced shallots. Cook the shallots until translucent; add the sliced potatoes and heat through. Add the spinach and season with salt and pepper. Cook until the spinach wilts, about 2 minutes. Transfer to a serving platter.
2. Preheat broiler. Place the trout, flesh side up, on oiled broiling pan. Season with salt, pepper and coriander seed. Broil for 3-4 minutes, until desired doneness. Squeeze lemon juice over the fish; sprinkle with chopped parsley. Transfer to a serving platter and place the fish over the spinach.