Bring a pot with about an inch of water to boil.
In a large bowl that can sit atop the pot without touching the water, whisk egg yolks and sugar together.
Once the water boils, turn off the heat and place the bowl over the pot to form a double boiler.
Keep whisking the egg mixture steadily until the sugar fully dissolves and the color turns pale, about 5 minutes.
Remove the bowl from the heat and immediately stir in the mascarpone cheese until the mixture is smooth and creamy.
In a separate bowl, combine whipping cream, matcha powder, and vanilla extract, then whip with an electric mixer until medium peaks form.
Gently fold the whipped cream into the mascarpone mixture until blended evenly.
For the matcha soak, whisk together matcha powder, sugar, and hot water in a shallow dish until slightly frothy, about 30 seconds.
Quickly dip each ladyfinger into the matcha soak, coating both sides lightly. Allow excess liquid to drip off and do not soak them fully to avoid sogginess.
Arrange a single, even layer of dipped ladyfingers at the base of a serving dish.
Spread a generous layer of the matcha mascarpone cream atop the ladyfinger layer and smooth it out gently.
Add another layer of dipped ladyfingers and repeat with another mascarpone cream layer.
Cover the tiramisu and refrigerate for a minimum of 4 hours, or preferably overnight, allowing flavors to meld and textures to set.
Just before serving, dust the top with matcha powder for a vibrant finishing touch.
