Mix strawberries with sugar, balsamic vinegar, vanilla and a pinch of salt in a glass bowl and let macerate for 1/2 hour. In a separate bowl, mix mascarpone with honey until well incorporated.
Preheat oven to 400 degrees. Unfold sheet of puff pastry onto a baking sheet lined with parchment and cut the puff pastry into 6 squares. With a sharp knife, lightly score the dough 1/2 inch from edges, creating a border. Try not to cut through the dough. Brush the border with egg wash or cream and sprinkle with sugar. Freeze or refrigerate for 10 minutes and then bake until golden, about 12-15 minutes. Let cool and then gently press center to flatten and create a bowl.
To assemble tartlets, spoon a dollop of mascarpone mixture into each shell and top with the macerated strawberries. Serve with a drizzle of the juice from the strawberries and a sprig of mint if desired. Serve immediately. Serves 6.