Beat the egg yolks, vanilla extract and 3/4 cup sugar with an electric mixer on high speed until thick and pale. Set aside.
In a separate bowl, beat the egg whites and salt with an electric mixer on medium speed until soft peaks form. Slowly add the remaining 6 tablespoons sugar and beat until stiff, glossy peaks form.
Gently fold the egg white mixture into the egg yolk mixture. Combine the flour, cornstarch and matcha green tea powder in a small bowl, then add to the egg mixture in 3 additions.
Line 2 baking sheets with parchment paper and spray with cooking spray. Divide the batter between the baking sheets and smooth the surface with a spatula. Bake at 350F for 10-15 minutes, until fully cooked. Transfer to a cooling rack and fully cool.
In the meantime, pour the matcha green tea ice cream into a deep dish lined with parchment paper. Return to the freezer to freeze until stiff.
Cut the sponge cake into circles with a round cookie cutter. Remove the ice cream from the dish and cut the ice cream into circles as well. Sandwich one disk of ice cream between two pieces of cake and enjoy! These can be stored in your freezer for future snacking.