Prepare the matcha mixture: In a small bowl, whisk together 2 tablespoons of sifted matcha powder and 1/2 cup of hot water until smooth. Let cool slightly.
If using, stir matcha liqueur or rum into the cooled coffee.
Lightly dip each ladyfinger into the coffee mixture and arrange in a single layer at the bottom of a 8x8 inch dish. Avoid soaking excessively.
In a large bowl, beat the cold heavy cream with an electric mixer until soft peaks form.
In a separate bowl, beat the mascarpone cheese and granulated sugar until smooth and creamy.
Gently fold the whipped cream into the mascarpone mixture until well combined. Be careful not to overmix.
Spread half of the mascarpone cream mixture evenly over the layer of ladyfingers.
Repeat layers: Dip the remaining ladyfingers in the coffee mixture and arrange over the cream layer. Spread the remaining mascarpone cream over the ladyfingers.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld and the tiramisu to set.
Before serving, dust the top generously with additional sifted matcha powder.
Cut into squares and serve chilled.
Optional Tips: For a richer flavor, use full-fat mascarpone cheese. If a thicker consistency is desired, consider adding a stabilizer like a teaspoon of gelatin dissolved in a tablespoon of cold water and then gently warmed before incorporating into the cream mixture. For a vegan version, use plant-based mascarpone and heavy cream alternatives. Ladyfingers can be substituted with sponge cake slices if needed.