Preheat oven to 400 degrees. In a small mixing bowl, combine the horseradish, lemon juice and zest, orange juice and zest, and cilantro. Season with sugar and salt. Season and oil both sides of the scallops. Lightly oil the cedar plank. Place the scallops on the planks and spread an even layer of the crust over the scallops. Place in the oven and bake for 6 to 8 minutes or until the crust is golden brown. In a large saute pan, heat the olive oil. Add the spinach and wilt for 3 to4 minutes. Stir in the shallots and garlic. Season with salt and white pepper. Remove the scallops from the oven. Mound the spinach in the center of the plate. Arrange the scallops around the spinach. Spoon the sauce around the plate. Garnish with long chives and chopped chives.