[Gâteau roulé matcha et azuki]
The thing that happens when you buy a big pouch of anko (Japanese sweetened red bean paste) to make strawberry daifuku is that you're likely to run out of rice flour long before you use up all the azuki paste.
I assume it keeps for weeks if well wrapped, but I didn't want to let it sit in the fridge for too long (shelf space is in short supply), so I tried to think up ways to use it. A quick brainstorm led me to the gâteaux roulés (cake rolls, a.k.a. jelly rolls or Swiss rolls) that my mother makes and sometimes garnishes with crème de marron, sweetened chestnut paste, which I've always felt is a close cousin to anko, texture- and flavor-wise. And since the pairing of green tea and red bean is always successful, perhaps I could flavor the cake with a little matcha*?
I opted to make the cake component (la génoise) butterless, using almond butter instead, and I cut the red bean paste with about a third of its weight in yogurt, to make the filling easier to spread and less intensely sweet.
Alhough I have stood by my mother (and held my breath) as she deftly rolled up layers of sponge cake, this was my first time actually making a cake roll of my own, and I was rather pleased with how it turned out: I did bake my génoise a tad too long, which resulted in crisp edges that I should probably have trimmed, but the heart of the cake was moist and tender, and the balance of flavors was just right. Not to mention, I was tickled to notice that each cut slice drew the hiragana character の (no), a feature few cakes can boast.
Because this was just a trial run for private consumption, I didn't decorate the cake, but I think a light-handed dusting of confectioner's sugar and/or matcha would accent the color of the cake nicely -- I picture oblique lines sifted through a simple homemade stencil. Next time I may also try brushing the cake layer with a light green tea syrup (possibly made with genmaicha for the toasted note ?) before spreading the filling.
What about you, how do you like your cake rolls?
* A quick online search revealed -- as I suspected, really -- that others had had the same idea, not the least of whom is Sadaharu Aoki, a Japanese pastry chef I was lucky enough to meet two years ago.
Matcha and Azuki Cake Roll
For the cake (génoise):
- 4 eggs, separated
- 40 grams (2 rounded tablespoons) almond butter (substitute 30 grams / 2 tablespoons butter, melted and cooled)
- 80 grams (6 tablespoons) sugar
- 75 grams (2 2/3 ounces or 2/3 cup) flour
- 25 grams (3 tablespoons) corn starch
- 6 grams (1 tablespoon) matcha (finely powdered green tea)
- a good pinch of salt
For the filling:
- 280 grams (10 ounces) anko (sweetened azuki bean paste; preferably tsubuan, which is a little chunky); if unavailable, substitute sweetened chestnut purée (crème de marron)
- 80 grams (1/3 cup) plain Greek-style yogurt or fromage blanc or crème fraîche
For the topping: (optional)
- confectioner's sugar
- matcha (green tea powder)
Prepare the cake. Preheat the oven to 200°C (400°F) and line a 35-by-25-cm (14-by-10-inch) jelly roll pan with parchment paper; I used my rimmed silicone mat, which of course doesn't need lining. (Alternatively, line a rimmed baking sheet with parchment paper, and draw a 35-by-25-cm [14-by-10-inch] rectangle on it lightly in pencil; you'll then spread the cake batter onto the paper into a rectangular shape, using the drawn-on shape as a guide.)
In a medium mixing bowl, combine the egg yolks with the almond butter and sugar. Beat well with a wooden spoon. In another bowl, sift together the flour, corn starch, and matcha. Stir the flour mixture into the egg yolk mixture until just blended, without overmixing.
Place the egg whites and the pinch of salt in a clean, grease-free mixing bowl, and whisk until stiff. Stir one third of the egg whites into the batter, then fold in the rest with a spatula, lifting the mixture to keep as much air as possible in the egg whites.
Pour the batter onto the prepared pan or sheet, making sure it reaches the corners, and smooth out the surface gently with the spatula. Bake for 6 to 8 minutes, keeping a close eye on it, until just set; it should not color.
While the cake is baking, prepare the filling: combine the anko and yogurt in a bowl, and stir well. Set aside.
Once the cake is baked, you have to work quickly while the cake is still warm, otherwise it will be too stiff to roll. Slide the parchment paper and cake on a cold baking sheet or a tray. Using a sharp knife, trim the edges of the cake if necessary to get a neat rectangle, or if the edges have gotten a bit crisp in the oven.
Cover with a clean dishtowel (or a fresh sheet of parchment paper, which you can reuse several times) and flip cautiously onto your work surface, so that one of the short edges is close to you. Remove the cold baking sheet or tray and carefully peel off the sheet of parchment paper on which the cake baked (or, in my case, the silicone mat). The cake will now be upside-down, the spongiest side facing the ceiling.
Spread the filling onto the cake, leaving a margin all around. Roll the cake tightly onto itself, starting from the edge closest to you. It will feel a little awkward at first -- you can use the dishtowel to help your grip -- but will get easier after the first few inches. Wrap the rolled cake tightly in the dishtowel and place it seam side down in the fridge to set for a few hours or overnight.
Just before serving, slice off the ends of the roll -- at an angle if you like -- for a neater look, place the cake on a serving dish, and dust with confectioner's sugar and/or a little matcha powder. Serve on its own, or with a dollop of yogurt. The leftovers will keep for a few days, well wrapped in the fridge.
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