In a large bowl or the bowl of your stand mixer, beat the whipping cream, powdered sugar, and cornstarch (if using) until stiff enough to hold soft peaks. Add the mascarpone and lemon curd to the bowl and continue to beat on medium-low speed until just combined.
Fill the trifle:
Pour the lemonade into a large shallow bowl. Quickly dip the ladyfingers in the lemonade, in and out just enough to wet them on both sides.
As you dip them, make a first layer at the bottom of the trifle bowl with the ladyfingers.
Spread a layer of lemon-whipped mascarpone over the ladyfingers. Arrange a single layer of strawberry slices over the top.
Continue soaking the ladyfingers in the lemonade and make another layer over the strawberries, topping them with the lemon-whipped topping and, again, strawberries on top.
Repeat, the ladyfinger-whipped strawberry layering to the top of the trifle, making a top layer of lemon-whipped mascarpone and a fresh berry on top.
Chill & Serve:
Chill the trifle for 1 hour, until ready to serve. Garnish with fresh berries and mint leaves.
Notes
*The cornstarch is optional; however, it's added to help the whipped cream retain its shape in the refrigerator, especially if making this dessert 24 hours in advance.