Charcoal Matcha Strawberry Roll Cake

I recently bought some activated charcoal since I saw so many places on IG using it! And then I saw a roll cake with matcha filling and knew I should try doing that! The filling was not stable enough to support the cake, so the cake sort of broke :(. I think actually rolling the cake like swirl may have been a better option. I also made a charcoal sablé and tried to incorporate it, but it really didn’t add much. That recipe was equal parts butter, granulated sugar, and almond flour with a tiny bit of charcoal heated in the oven until baked.

1. Charcoal Sponge: (one jelly roll sheet)

• 112g cake flour
• 1 tsp baking powder
• 1/4 tsp salt
• 5 large eggs, separated
• 156 g granulated sugar
• 60 g whole milk
• 10 g activated charcoal

1. Preheat oven to 400F. Line baking sheet with parchment paper or silpat.
2. Whisk together sifted flour, baking powder, salt, and charcoal. The charcoal will get everywhere, so add and mix it slowly.
3. In a different, large bowl, whisk egg yolks, sugar, and milk until pale.
4. Separately, whisk egg whites until medium stiff peaks (if you whisk too stiff, it’s harder to incorporate).
5. Add dry mixture to wet mixture and fold together. Then slowly fold in the medium stiff egg whites. Be careful not to deflate them too much.
6. Pour batter onto the baking sheet and then rap the sheet down a few times to release any big air bubbles.
7. Bake for 8-9 minutes (a toothpick should go in and out cleanly).
8. Invert cake, remove silpat or parchment paper and let cool.Whichever side is nicer, let that side be the outside of the roll (bottom).
9. Let cool.

2. Matcha Diplomat Cream minus gelatin: (Note: I actually don’t know what it’s called..but I think this?)

• 4 large egg yolks

• 37 g cornstarch

• 340 g milk

• 100 g sugar

• 8 g matcha

• 225 g heavy cream

• 10 g powdered sugar

• 4 g matcha

1. You need to make a custard and a whipped cream. Take your large bowl and whisk that you’re going to make the whipped cream with and throw that into the fridge before you begin. You want it cold.
2. First prepare custard component. In a large bowl, combine egg yolks and cornstarch.
3. In a saucepan, high heat, combine milk, sugar, and matcha.
4. Bring to boil and remove from heat.
5. While whisking constantly, slowly add to bowl with yolks and cornstarch. You are tempering the egg yolks so that they won’t scramble.
6. Return the mixture to the saucepan on high heat.
7. Bring to rolling boil, while whisking/ mixing constantly. The mixture will become custard  like. I use a hand blender instead of a whisk and it works super well!
8. If it is not smooth, sieve through a fine mesh into a bowl and cover the bowl with cling wrap. Make sure to press it directly onto the custard to avoid condensation.
9. Chill.
10. Now prepare whipped cream component. Take out the chilled bowl, whisk, and cream. 
11. Add cream and powdered sugar and whisk until firm peaks.
12. Take out the matcha custard and whisk a bit to loosen it up. Add a small amount of whipped cream to lighten the mixture even more.
13. Slowly fold in the rest of the whipped cream, making sure not to overfold (will deflate the cream).

3. Assembly:

• 5 - 10 g coursely crushed dehydrated strawberries (bought from Trader Joe’s) [I used a whisk to smash]
• a few strawberries, pureed and sieved

1. For this particular roll, I removed a rectangle from the sheet pan and left a square. Cut a small corner of the sheet off like: |________| ---> /________\ (helps with rolling)
   
2. Add a layer of matcha diplomat cream and then sprinkle some crushed dehydtaed strawberry. I also piped out some of that puree.
   
3. I added another layer of matcha cream then using the parchment paper or silpat that the cake had cooled on to help, slowly roll the cake onto itself.
4. Maintain the shape until fully rolled then wrap up the cake in saran wrap and place in fridge to chill.
5. Dust and sprinkle with crushed dehydrated strawberries strawberries.

Additional Thoughts

1. Adding some gelatin or agar agar into the diplomat cream would probably provide the stablity it needed to hold.

Gluck,
-Mario