To cook the scallops
Trim away the tough muscle from the side of each scallop, then set aside at room temperature. Wash the salad greens, dry well, and combine in a bowl. Dress with the lemon zest and juice and the extra virgin olive oil, then divide among four plates or arrange on a large platter.
Place two heavy (ideally, nonstick) skillets over high heat and allow them to get very hot. Season the scallops lightly with salt and pepper. Drizzle 1/2 Tbs. olive oil into each skillet.
When the oil begins to smoke, add the scallops, arranging them in a single layer. It is important not to overcrowd the skillet (if you do, the scallops will stew rather than pan-fry), so cook in two batches if necessary. Cook for 1 minute only, then turn (in the same order that you put them into the pan) and cook for the same amount of time on the other side. The scallops should be crunchy and golden on the surface, with a sweet and delicious taste.
As you remove the scallops from the pan, place them on top of the salad greens, adding a dollop of horseradish cream. Sprinkle with minced parsley and serve straight away, with a wedge or two of lemon on the side.
You can make the horseradish cream up to a day in advance. Cover and refrigerate, but return to room temperature before serving.