Soft and fluffy matcha Swiss roll cake filled with sweet red bean paste is wrapped in bread dough and baked. The result is a cake wrapped in bread. It is a hybrid of bread and cake in one bite! The recipe is available for sourdough version as well.
Decide if you want to make the cake the day before or you want to bake the cake on the same day you prepare the bread dough
Prepare SSS for sourdough version:
About 4-5 hours before you plan to make the bread, combine all ingredients for the stiff starter in a bowl. Stir a bit to roughly combine and then use your clean hand to knead it. This is a stiff starter, it's like dough. Make sure no pockets of dry flour are visible. Transfer to a large see-through container (plastic or glass is fine, preferably wide-mouth so you can get it out easier later). Loosely cover with the lid and let it ferment until triple in size
Cut into little pieces when it is ready to be used. It mixes more easily into the dough
Preheat oven to 350 F (180 C) for a conventional oven. Lower the temperature by 20 F or 15 C for a convection oven
Spray the baking pan, 9 x 13 x 1 inch, with non-stick cooking spray or brush some oil and then line with a parchment paper on the bottom and the side
Prepare the cake batter:
In a large mixing bowl, whisk egg yolks, oil, milk until combined. Sift in the cake flour, matcha powder, and salt. Whisk to mix until combined and no lumps
Prepare the meringue:
Make sure the egg whites are at room temperature. Place egg whites in a mixing bowl of a stand mixer fitted with a whisk attachment. Whisk until foamy on medium speed and then add lemon juice/vinegar and whip again for another minute then and 1/3 of the sugar and continue to add sugar until you use it all up. Whip until the egg white develops a medium-soft peak. When you lift the meringue up it will hold up its shape but the tail will bend. Do not whip until stiff peak. The cake will crack when you roll it later
Combine meringue with cake batter:
Fold about 1/3 of the meringue into the egg yolk batter and use a rubber spatula or whisk to fold or whisk until mix and continue to fold in the next 1/3 until you use up all the meringue and the batter is smooth . The batter should be a pourable consistency
Pour into prepared baking pan:
Fold about 1/3 of the meringue into the egg yolk batter and use a whisk to fold and continue to fold in the next 1/3. Switch to a rubber spatula for the last 1/3. The spatula helps to scrape the bottom and the sides of the bowl to make sure everything is folded in evenly. The batter should be a pourable consistency
Bake:
Gently tap the baking sheet on your working surface several times to pop any air bubbles. Bake in a preheated oven for 30 minutes and then switch to convection mode (fan mode) and bake for another 3-4 minutes or until the top is golden brown and dry to touch. If you don't have convection mode, bake another 5 minutes and check to make sure the top is golden brown and dry to touch. It is important that the top is dry to touch so this layer won't peel off when you roll later
Cool down:
Remove the cake from the oven and then lift it out from the pan immediately to a cooling rack and peel off the parchment paper from 4 sides. This helps to prevent wrinkles on the surface. Let it cools down like this for 5-6 minutes (I use a timer to actually time it)
After 5-6 minutes. Place a new piece of parchment paper, larger than the cake, on top of the cake and flip over to the other side. Peel off the parchment paper
Assembling the cake:
Use a serrated knife to trim about 1/4-inch of the 4 edges
Use a serrated knife to make 4 shallow slits. about 1 inch apart, taking care not to cut through the cake. This makes rolling the cake easier
Mound the filling a bit off the middle, kinda nearer to your side
Very gently use one hand to lift the parchment paper up to help you roll the cake up until you reach the other side. Tuck the parchment paper under and use a dough scraper to help you tighten the roll-up
If you are preparing the cake the day before, wrap it well in a cling wrap and put inside a zipper bag, push all the air out and seal. It can be kept at room temperature.
Prepare the bread dough:
Mix all the dry ingredients together in a mixing bowl. Make a well in the center and pour in the wet ingredients and the stiff starter for sourdough version. Use a dough hook attachment to knead the dough on speed 2 until all the crumbly dough starts to come together into one mass, it may take about 2-3 minutes for this to happen. Don't be tempted to add any liquid. You may need to stop halfway and scrape the dough off the hook and the sides of the bowl and knead again for another 3 minutes
Gradually add in the softened butter bit by bit. The dough will turn into a sticky mess again because of the butter, just keep kneading and stop halfway and scrape the dough off the hook and bowl again and continue to knead until the butter is absorbed by the dough. IT WILL HAPPEN, don't worry! DO NOT be tempted to add any extra flour. You will get a shiny smooth dough that is very elastic. This may take about 5-8 minutes on speed 4, depending on your mixer too. The dough must pass a windowpane test, meaning, when you stretch a small amount of dough thinly, it won't break and a light can pass through
1st proofing:
Place this dough in a lightly oiled large bowl, cover it with a clean and damp tea cloth or plastic wrap and let it rise at a warm place. If you use commercial yeast, this may take about 1 hour or longer depending on temperature. If you use a sourdough starter, proof for 2 hours. The dough may not double for sourdough version but that's okay, we are not aiming for double with sourdough. If you use commercial yeast, the dough has clearly almost doubled or doubled in size
When you poke the dough with your lightly-floured finger, the indentation stays and the dough doesn't collapse.
Shape:
Line a large baking pan with parchment paper
Degas the dough by punching it down and then divide into 12 doughs, roughly the same size or weight. Cover and let them rest for 15 minutes to relax the gluten.
Roll each one into a strip, enough to wrap around the Swiss roll cake (as shown in the photo). Lay the strips down on a baking pan and then put the roll cake on top of the strips, seam side up. Bring the end of two strips together and pinch to seal. So the strips are wrapped around the Swiss roll cake
Gently flip over the dough-wrapped cake so the seam side is down now.
Final proofing:
Let it ferment at a warm place, about 82-86 F (28-30 F) until they are noticeably puffy and fill up the gap. This may take 1-2 hours if you are using yeast and about 3-3 1/2 hours for sourdough version
If you gently press on the dough, it will bounce back very slowly and leave an indentation. If it bounces back right away, proof a bit longer
Baking:
10 minutes before the end of proofing, preheat the oven to 375 F (190 C)
Combine egg with milk to make the egg wash. Make sure you whisk the egg really well. Brush on top of the bun
Place the pan on the middle rack and bake for 12-15 minutes or until golden brown or the inner temperature is 190 F. Do not overbake as it will dry out the crumbs and also the cake. I highly recommend a digital thermometer if you bake often as it helps to clear out that doubt whether the bread is baked through or not
Remove from the oven and let them cool down on cooling rack
Serving:
Let the bread cool down completely before serving. Trim both ends so it looks neat. Slice into desired size and serve
Leftovers can be kept at room temperature in an air-tight container for 2-3 days