Sift 2 tablespoons of matcha powder into a wide, shallow bowl. Pour in the hot water and whisk vigorously until fully dissolved and slightly frothy. Set aside to cool completely.

Create a double boiler: simmer 1 inch of water in a saucepan. In a heatproof bowl that fits over the pan (without touching the water), combine egg yolks and 1/4 cup sugar.

Place the bowl over the simmering water and whisk continuously for 5-7 minutes until the mixture is pale, thick, and reaches 160°F (71°C). Remove from heat and let cool for 5 minutes.

Gently fold the room-temperature mascarpone cheese into the slightly cooled yolk mixture until completely smooth and velvety. Do not overmix.

In a separate chilled bowl, whip the cold heavy cream and the remaining 1/4 cup of sugar until it holds medium-firm peaks.

Gently fold the whipped cream into the mascarpone mixture in two batches, using a figure-eight motion to keep the cream light and fluffy.

Quickly dip each ladyfinger into the cooled matcha liquid for exactly one second per side. Arrange a tight, single layer of soaked ladyfingers in the bottom of an 8x8-inch dish.

Spread exactly half of the mascarpone cream evenly over the first layer of ladyfingers.

Repeat with a second layer of quickly-dipped ladyfingers, followed by the remaining half of the mascarpone cream. Smooth the top perfectly flat.

Cover tightly with plastic wrap and refrigerate for a minimum of 4 hours, preferably overnight, to allow the layers to set.

Right before serving, place the remaining 1 tablespoon of matcha powder into a fine-mesh sieve and evenly dust the entire surface of the chilled dessert. Cut into squares and serve.