Slice the tomatoes and mozzarella ¼ inch thick. If you are using buffalo mozzarella, gently press the sliced cheese between two paper towels to remove the excess moisture.
If you do not have a good quality aged balsamic vinegar on hand, you can create a balsamic reduction by adding your desired amount (at least ½ cup) of balsamic vinegar to a medium sauce pan over medium-low heat. Stirring occasionally, heat 10 – 20 minutes or until the vinegar as thickened. Do not let it reduce down too much, or you will end up with a chewy molasses-like texture.
Alternately arrange the tomato and mozzarella slices on a plate. Drizzle with balsamic vinegar and basil oil. Season with salt and pepper to taste.