• This cake is best served cold. So I recommend to assemble the cake the day before you plan to serve this cake. Some parts of the recipe can be prepared few days before, which I recommend, so you won't feel overwhelmed

Prepare the matcha pastry cream: (can be prepared a few days before)

• In a saucepan, combine whole milk, cornstarch, sugar, matcha powder, and egg yolks. Whisk until smooth.
  
• Put them on the stove over medium-low heat and keep whisking until they start to boil and bubble. Cook until the mixture is thick. Turn off the heat and add the butter and vanilla extract and whisk until the mixture is smooth. Cover with cling wrap, touching the cream directly to avoid skin from forming. Keep it in the fridge or up to 3 days if you make this ahead
  

Prepare easy feulletine (if you choose to make your own):

• Preheat the oven to 350 F (180 C) for conventional oven. Lower the temperature by 20 F (15 C) if using convection oven.
• Use silicone mat if you have one. It's so much easier to spread the batter thinly. Place the silicone mat on top of an upside-down baking pan (I use a half-sheet pan (18 x 13 inches, because the silicone mat fits perfectly). You will need to bake in two batches to achieve the thin and crispy texture
• Combine melted butter (no longer hot), sugar, egg whites, a pinch of salt, baking soda, and vanilla in a bowl. Whisking until the mixture combines. Add all-purpose flour and whisk until the mixture is smooth. It will be semi-thick but still spreadable in consistency
• Spread half of the batter very thinly on the silicone mat using an offset spatula. Make sure to spread it evenly throughout. Usually the center tends to be thicker, so try to spread it out as evenly as possible so they bake evenly
  
• Place the baking pan in the middle rack in the oven and bake for 8-10 minutes, rotate the pan halfway through baking. It should be golden brown and even in color. The center part tends to be a bit lighter in color, but that's okay
• The feulletine appears very soft at this point and don't try to remove it from the silicone mat or parchment paper yet. Leave the baking pan on a cooling rack to let it cool down for 15 minutes or so.
  
• You will be surprised by how crispy it has become. Gently peel it off of the mat or parchment paper.
  
• Break it into large pieces and store it in an air-tight container if it has cooled down completely. They can be stored for about a week or so if a cool dry place
  

Prepare the matcha cake:

• Preheat the oven to 350°F (180°C). Oil an 8 x 8 inch pan then line an 8×8-inch pan with parchment paper sling.
• Combine matcha powder with hot water to make a thick paste. In a bowl, whisk together flour, baking powder, baking soda, and salt. In a separate bowl, whisk matcha paste, sugar, oil, and egg until combined. Add yogurt, milk, and vanilla; whisk until smooth.
  
• Add dry ingredients to wet and whisk gently until just combined (don’t overmix).
  
• Pour into prepared pan, smooth the top, tap the pan on the counter a few times to pop any air bubbles trapped inside the cake. Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean.
  
• Let it cool in the pan for 10 minutes, then lift out to a wire rack. Cool completely before assembling the cake
  
• If the cake has hump, you can cut it off with a serrated knife to make the surface more even

Assembling the cake:

• I put the cake back into the pan. Poke some holes on the surface of the cake using a toothpick or a tip of a small knife. Use a pastry brush to brush heavy cream on top of the cake.
  
• Get the matcha cream out of the fridge. Use a spatula to fold and mix the cream again to get it back to a smooth consistency if you have made it a few days before. Spread the cream evenly on top of the cake. Offset spatula help to spread it evenly
  
• Keep the cake chilled in the fridge when you melt chocolate for the feulletine
• Fill up a saucepan with some water. Put chopped up white chocolate and oil in a heat proof bowl set on top of a saucepan. Make sure the bowl is not touching the water. Put this on the stove over medium-low heat and stir until chocolate melts. Remove from the heat and let it cool down a bit, Because of the oil, the white chocolate will set a bit softer later, which is what we want
  
• Place the feulletine in a mixing bowl. Pour the melted white chocolate in and use spatula to mix.
  
• The process of mixing will break up the feulletine into smaller pieces. Combine until all feulletine is coated with chocolate
  
• Get the cake out from the fridge and spoon the feulletine on top of the matcha pastry cream. Use a rubber spatula or the back of the spoon to help you spread out the feulletine mixture evenly across the cake
  
• Put the cake back into the fridge for at least 1 hour or overnight to let the feulletine layer set and harden

When ready to serve:

• This is not meant to be a "neat" cake you can cut with a knife. Use a spoon to gently crack and break the feuilletine layer and scoop out some servings onto a serving plate. You will have all three layer, the matcha cake, the cream, and the crunchy feulletine layer. You are not dreaming! It's a dream cake you can really eat!