Pour the balsamic vinegar into a saucepan and reduce over high heat until thickened and syrupy, about 10-15 minutes. Remove from heat and let cool to room temperature, about 10 minutes.
Quarter the strawberries.
Toss the quartered strawberries lightly with the sugar to coat.
Combine the sweetened strawberries, cooled balsamic reduction, and toasted pine nuts in a bowl.