In a medium bowl, combine the sliced strawberries with granulated sugar. Toss gently and let sit for 10-15 minutes until they release their juices.
In another bowl, use an electric mixer to whip the heavy cream until it starts to thicken. Gradually add powdered sugar and vanilla extract, and continue whipping until soft peaks form.
If using sponge cake, slice it into rounds. If using ladyfingers, you can use them whole.
In a 9x13 inch baking dish, start layering: place a layer of sponge cake or ladyfingers at the bottom.
Spoon a layer of the whipped cream mixture over the cake, spreading it evenly.
Add a layer of the macerated strawberries on top of the whipped cream, including some of the strawberry juice for added flavor.
Repeat the layers: cake, whipped cream, and strawberries until the dish is filled, finishing with a layer of whipped cream on top.
Cover the dish with plastic wrap and refrigerate for at least 4 hours or preferably overnight to allow the flavors to meld and for the cake to soften.
Before serving, garnish with fresh mint leaves and a few extra strawberry slices for decoration.
Notes
For best results, refrigerate overnight to enhance flavor.