Whisk together preserves and juice: In a wide bowl, whisk strawberry preserves and orange juice, set aside.
Mix whipped cream: Using an electric mixer, beat chilled whipping cream, sifted powdered sugar, and vanilla extract in a large bowl to soft peaks.
Prepare mascarpone filling: Place mascarpone in another large bowl and stir in ½ of the whipped cream mixture to lighten. Fold in remaining whipped cream mixture, until smooth and velvety.
Prepare strawberries and ladyfingers: Hull and slice half of the strawberries (the rest will be sliced at time of serving). Dip the ladyfingers in the strawberry and orange juice mixture on both sides to coat entirely. Once dipped, place on the bottom of an 11 x 8 dish or equivalent. Arrange enough dipped ladyfingers to cover the bottom of the dish.
Layer and repeat: Spread half of the mascarpone filling over the top, followed by the sliced strawberries in an even layer. Repeat with one more layer of dipped ladyfingers and pour the remaining preserve mixture over. Top with the rest of the mascarpone filling in a nice even layer.
Cover and chill: Cover with plastic wrap and chill overnight (at least 8 hours).
Top with fresh strawberries and serve: Hull and slice the rest of the fresh strawberries. When ready to serve, arrange neatly over the top of the tiramisu.