We tried substituting regular balsamic vinegar for aged balsamic vinegar but found the taste too sharp and pungent.
Bring first 5 ingredients to a boil in a saucepan over medium-high heat; reduce heat to medium, and simmer 6 to 7 minutes or until mixture is reduced by half. Remove from heat; stir in cognac, if desired. Serve warm.
Note: For testing purposes only, we used Alessi 20-Year Balsamic Vinegar aged in wood.