Prepare the Sponge Cake

1. Preheat Oven: Preheat your oven to 350°F (175°C). Line a 10×15-inch jelly roll pan with parchment paper.
2. Separate Eggs: In two bowls, separate the egg whites from the yolks.
3. Beat Egg Yolks: In a medium bowl, whisk egg yolks with half of the sugar until pale and thick. Add oil and milk, whisking until combined.
4. Sift Dry Ingredients: In another bowl, sift together flour, matcha powder, baking powder, and salt. Gradually fold the dry mixture into the yolk mixture.
5. Beat Egg Whites: Using an electric mixer, beat egg whites until soft peaks form. Gradually add the remaining sugar and beat until stiff peaks form.
6. Combine Mixtures: Gently fold the egg whites into the yolk mixture in three batches, being careful not to deflate the batter.
7. Bake: Pour the batter into the prepared pan, spreading evenly. Bake for 10-12 minutes, or until the cake springs back when lightly touched.
8. Cool the Cake: Lay a clean kitchen towel on your counter and dust with powdered sugar. Turn the cake out onto the towel, peel off the parchment paper, and roll the cake (with the towel) while warm. Let cool completely.

Prepare the Filling

1. Whip the Cream: In a chilled bowl, beat heavy whipping cream, powdered sugar, matcha powder, and vanilla extract until stiff peaks form.
2. Set Aside: Keep the filling refrigerated until ready to use.

Assemble the Roll Cake

1. Unroll the Cake: Once cooled, carefully unroll the cake and remove the towel.
2. Add Filling: Spread an even layer of the matcha whipped cream over the cake.
3. Roll Again: Gently re-roll the cake, using the parchment paper to help shape it.
4. Chill: Wrap the rolled cake in plastic wrap and refrigerate for at least 30 minutes to set.