In a small saucepan, combine the balsamic vinegar, sugar and lemon juice. Bring the syrup to a boil over a low flame and reduce the liquid to about 1/4 cup. Set the syrup aside to let it cool completely.
Place the cut strawberries in a bowl, if they are not very sweet add a scant tablespoon of sugar. Drizzle the balsamic glaze over the berries, toss gently and let stand for about 15-20 minutes, stirring occasionally.
Combine the chilled mascarpone cheese, heavy cream and vanilla in a bowl of a standing mixer fitted with a whisk attachment, or use a hand mixer. Whisk the cream until stiff peaks form. Divide the berries coated in syrup over 4 clear bowls or glasses, alternating layers of berries and whipped cream. Serve with a sprinkle of fresh chopped mint.