An easy elegant appetizer which can all be made ahead of time. The onions, garlic oil, and horseradish cream can all be made and refrigerator until you are ready to put them all together. Then, just a few minutes to grill the bread ... add your toppings and serve. Serve these with along with a few dips/spreads or other appetizers and a big pot of soup to friends, and you have a great easy party.