Mix together the mayonnaise and Basil Pesto Sauce and spread evenly on one side of each slice of bread
Layer the tomato, salami, mozzarella, and basil on each sandwich and cook on a lightly greased panini press, or on a lightly greased grill pan with another heavy pan on top, about 5-10 minutes or until toasted as desired. If using a grill pan, flip the sandwich halfway through cooking.
Meanwhile, heat the balsamic vinegar in a small saucepan over medium-high heat until reduced and thickened.
Once the sandwiches are toasted, remove from panini press and drizzle with balsamic reduction.
