Matcha Roulade with Buttercream Filling

Preheat the oven to 175°C (approximately 350°C). 

For the sponge, separate the eggs and beat the whites with the salt and the lemon juice until stiff. Mix the yolks with the sugar and vanilla sugar until fluffy. Mix the flour with the matcha powder. Fold the egg whites into the egg yolks and then sift the flour and matcha over the egg mixtures. Gently fold until smooth. Spread into a 30 x 40 cm (approximately 11 x 15 inches) pan that has been greased and lined with parchment paper. Bake for 10-15 minutes, until lightly brown. Immediately turn out onto a cotton kitchen towel that has been sprinkled with sugar. Remove the parchment paper and roll the cake tightly with the cloth. Let cool, resting the cake on the seam side down.

For the filling, cook the pudding mix, sugar, and milk into a pudding according to the package. Allow to cool, stirring occasionally. Once the pudding is the same temperature as the butter, beat the butter in an electric mixer on high. Gradually add in the pudding and beat until light and fluffy.

Mix the cocoa powder with the heavy cream.