Let the biscuits cool completely on a wire rack before proceeding; you don’t want them to be hot, or the whipped cream will melt.
Meanwhile, wash and prepare the fruit as needed. Toss with 1 tablespoon of the sugar, or more or less to taste, and let sit while you whip the cream. Whip the cream until it holds soft peaks, then slowly add the remaining sugar and the vanilla and whip for until it forms peaks as soft or firm as you like, 1 or 2 minutes more.
Split the biscuits and fill them with cream and fruit. Serve right away.