Prepare the ladyfinger crust:
Crush ladyfingers and combine them with melted butter.
Press the mixture into the bottom of a 9x9-inch dish and refrigerate for 30 minutes.
Make the mascarpone filling:
Whip mascarpone cheese and powdered sugar until smooth.
In a separate bowl, whip heavy cream until soft peaks form.
Gently fold whipped cream into mascarpone mixture.
Prepare the espresso soak:
Brew espresso and let it cool.
Stir in coffee liqueur (if using).
Assemble the tiramisu:
Quickly dip each ladyfinger into the espresso, layering them on top of the crust.
Spread half of the mascarpone mixture over the soaked ladyfingers.
Repeat with another layer of soaked ladyfingers and mascarpone mixture.
Smooth the top and refrigerate for 3 hours.
Finish the dessert:
Before serving, dust with cocoa powder.