The matcha powder can be dissolved in hot creamer or water instead of the milk.
For Step 4, if you are using granulated sugar instead of superfine, place a small pot of water on the stove and heat until simmering. Place your egg yolks in a metal bowl and pour in the sugar. Move the mixing bowl above the simmering water. Make sure the bottom does not touch the water. Gently whisk the sugar and yolks together for 2 minutes until all the sugar dissolves. Repeat in Step 5 but with the egg whites.
For the filling, feel free to substitute milk for the heavy cream.