In a large bowl, combine the room temperature mascarpone and powdered sugar. Mix them together until they are well combined.
In a separate bowl, whip the chilled heavy whipping cream until soft peaks form.
Gently fold the whipped cream into the mascarpone mixture until fully incorporated.
PREPARE SOAKING LIQUID
Combine the orange juice with ½ cup of the orange liqueur. Stir well.
ASSEMBLE THE TIRAMISU
Quickly dip each ladyfinger into the soaking liquid, ensuring they're wet but not soggy.
Arrange a layer of the soaked ladyfingers at the bottom of your serving dish.
Spread half of the mascarpone cream over the ladyfingers.
Spread half of the strawberry preserve on top of the cream.
Arrange half of the sliced strawberries on top of the preserve.
Repeat the process with another layer of soaked ladyfingers, cream, preserve, and strawberries.
FINISH AND CHILL
Drizzle the remaining ¼ cup of orange liqueur over the top of the dessert.
Cover the dish with plastic wrap and refrigerate for at least 2 hours or overnight if possible. This will allow the flavors to meld together and the ladyfingers to soften.