Pour the bottle of balsamic vinegar into a heavy bottomed saucepan. Bring up to a boil and reduce heat slightly. There should be bubbles, but it shouldnt be a fully raging boil. Reduce the amount of vinegar by 80%. Dont over reduce, as it will thicken as it cools. Set the vinegar aside to cool and store in an airtight container.
Meanwhile, hull and clean the strawberries, slice in half and arrange is small serving dishes.
Add a heaping tablespoon of mascarpone on top of the strawberries. Drizzle the reduced balsamic syrup over the fruit and cheese.