Step 1: In a shallow bowl, whisk 2 tablespoons of matcha powder with the hot water until no clumps remain. Allow the liquid to cool to room temperature.
Step 2: In a large mixing bowl, beat the cold mascarpone cheese with granulated sugar and vanilla extract until smooth and creamy.
Step 3: In a separate chilled bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture until fully combined.
Step 4: Briefly dip each ladyfinger into the matcha liquid for about 1 second per side. Do not over-soak.
Step 5: Arrange a layer of soaked ladyfingers in the bottom of an 8x8 inch dish or similar glass container.
Step 6: Spread half of the mascarpone cream mixture over the ladyfingers, smoothing it out with a spatula.
Step 7: Repeat with another layer of soaked ladyfingers and the remaining cream.
Step 8: Cover and refrigerate for at least 6 hours, or preferably overnight. Just before serving, sift the remaining matcha powder over the top.