Step 1: Prepare the matcha soaking liquid by sifting 1.5 tablespoons of matcha powder into a bowl and whisking it with the hot water until smooth. Set aside to cool completely.
Step 2: In a heat-proof bowl over a pot of simmering water (double boiler), whisk the egg yolks and sugar together for about 5-8 minutes until thick, pale, and doubled in volume. Remove from heat and let cool.
Step 3: Gently whisk the room-temperature mascarpone into the cooled egg mixture until smooth and no lumps remain.
Step 4: In a separate bowl, whip the cold heavy cream and vanilla extract until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture in two batches.
Step 5: Quickly dip each ladyfinger into the cooled matcha tea and arrange a single layer in the bottom of an 8×8 inch dish.
Step 6: Spread half of the matcha cream over the ladyfingers. Repeat with another layer of dipped ladyfingers and the remaining cream.
Step 7: Cover and refrigerate for at least 6 hours, or preferably overnight. Dust generously with extra matcha powder right before serving.