Prepare the Matcha Mixture:
Sift 3 tbsp matcha powder into a bowl.
Whisk with 1 cup of warm milk or water until smooth and lump-free. Let it cool.
Make the Zabaglione:
Combine 4 egg yolks and 1 cup sugar in a heatproof bowl.
Place over a double boiler and whisk until thick and pale (about 5 minutes). Remove from heat.
Prepare the Mascarpone Cream:
Fold the mascarpone into the zabaglione until smooth.
Gently fold in the whipped cream to create a light, fluffy mixture.
Assemble the Tiramisu:
Briefly dip each ladyfinger into the cooled matcha mixture.
Layer the ladyfingers in a rectangular dish.
Spread a layer of mascarpone cream on top.
Repeat the layers until all ingredients are used, finishing with mascarpone cream on top.
Chill:
Cover the dish and refrigerate for at least 6 hours or overnight for the best flavor.
Garnish and Serve:
Dust with additional matcha powder before serving.
Garnish with fresh mint leaves or white chocolate shavings if desired.