Brush the bread slices with the olive oil and toast them in a skillet or under the broiler until lightly toasted. Alternately, toast the bread in a toaster and immediately drizzle with olive oil.
Place the arugula down on one slice of bread and top with the slices of tomato. Season well with salt and freshly ground black pepper.
Place the slices of fresh mozzarella on the tomatoes and season again with more salt and freshly ground black pepper.
Drizzle the balsamic vinegar on the mozzarella cheese and top with the leaves of basil.