Dissolve 3 teaspoons matcha powder in hot water to make a syrup; let cool. In large mixing bowl, whisk mascarpone with powdered sugar and vanilla. Add 2 teaspoons matcha and whisk until blended; set aside. With an electric mixer whip the cream to a stiff peak. With a spatula, fold in 1/3 of the whipped cream to the mascarpone mixture. Fold in the remaining whipped cream; set aside.
Place lady fingers in a single of a 9 x 13 inch glass baking pan. Generously brush each lady finger with matcha syrup. Evenly spread 1/2 cup of the azuki beans over the lady fingers; cover with 1/2 of the cream mixture; repeat. Cover with plastic wrap and refrigerate for at least 4 hours. Cut into pieces and dust with optional matcha powder before serving. Makes 12 servings.
Approximate Nutrient Analysis per serving:
450 calories, 29 g fat, 16 g saturated fat, 180 mg cholesterol, 100 mg sodium, 41 g carbohydrate, 1 g fiber, 8 g sugar, 90 g protein