Prepare Creamy Caramelized Onions. Adjust oven rack so it is about 5 inches from the heat. Preheat broiler.
Brush one side of each bread slice with oil. Place half of the bread slices on a large baking sheet. Broil for 1 to 2 minutes or until lightly toasted. Remove from oven. Turn bread slices over to use for bottoms of sandwiches. Divide corned beef and the caramelized onions among bottom slices of bread; add cheese. Broil for 2 to 3 minutes more or until heated through and cheese starts to melt. Transfer to a serving platter.
Place the remaining bread slices on the baking sheet. Broil for 1 to 2 minutes or until lightly toasted.
Spoon a small amount of salad dressing onto the bottom of each sandwich. Top with the remaining bread slices. Makes 16 appetizers.
Creamy Caramelized Onions
Preheat oven to 375 degrees F. In a large heavy ovenproof skillet, heat olive oil over medium-high heat. Add onions, cook for 8 to 10 minutes or until lightly browned, stirring frequently. In a small bowl, combine whipping cream; dry sherry; Dijon-style mustard; brown sugar; garlic; salt; ground allspice; and ground black pepper. Pour mixture over onions; stir to combine. Bake about 30 minutes or until golden brown and bubbly.