Directions

• Prep Work
• Whisk the ingredients for Group A together in a small cup.
• Mix the 10g of sugar and 20g of hot water together to make your simple syrup; let it cool.
• Line your baking dish smoothly with parchment paper.
• Set your oven rack in place and preheat your oven to 190°C (375°F).
• Whipping the One-Egg Sponge
• Crack the egg into a medium mixing bowl, break it up with an electric hand mixer, and add the 15g of granulated sugar. Place the bowl over a double boiler (hot water bath around 50–60°C) to gently warm the egg while whisking. Once the egg mixture reaches body temperature, remove it from the water bath.
  Continue whipping on high speed until the batter becomes pale, thick, and velvety, holding its shape beautifully when you lift the beaters.
• Folding and Incorporating
• Sift the cake flour directly into your whipped egg. Use a rubber spatula to gently fold the flour in using a sweeping, scooping motion just until the dry pockets disappear. Take a single large scoop of this batter and stir it directly into your bowl of Group A until smooth, then pour that mixture back into the main batter bowl and fold everything together gently until uniform.
• Baking the Sheet
• Pour your smooth batter into the prepared parchment-lined baking dish. Use a pastry scraper or spatula to level the surface completely flat, then give the bottom of the dish a gentle tap against the counter to release any large trapped air bubbles. Bake at 190°C (375°F) for about 10 minutes.
• Cooling the Sponge
• As soon as it finishes baking, lift the sponge out of the dish using the parchment paper edges and transfer it to a wire cooling rack. Gently peel the paper away only from the sides of the cake, then loosely drape a sheet of plastic wrap over the top of the sponge to keep it from drying out as it cools to room temperature.
• The Rich Matcha Cream
• While the cake cools, prepare your filling. In a medium mixing bowl, combine the heavy cream, 10g of sugar, and your sifted 10g of matcha powder. Place the bottom of the bowl over ice water and whip the mixture with your hand mixer until it forms stiff, stable peaks (8-turn cream). Keep it chilled in the fridge until ready to assemble.
• Prepping to Roll
• Once the sponge is completely cool, flip it over onto a clean sheet of parchment paper and carefully peel the bottom baking paper completely off. The golden-brown baked top of the cake should now be facing down against your new paper. Use a sharp knife to trim the far edge (the end you will roll towards) at a slight diagonal angle, this helps the roll close cleanly. Use a pastry brush to evenly moisten the entire surface of the sponge with your prepared sugar syrup.
• Filling and Rolling
• Spread your lush matcha cream evenly across the sponge using a spatula or scraper. Aim to make the cream slightly thicker at the edge closest to you and thinner toward the far diagonal-cut edge.Carefully lift the parchment paper from the side closest to you and roll the sponge upward and away from you into a tight cylinder.
• The Final Chill
• Wrap the parchment paper tightly around the rolled cake. To ensure a perfectly tight, round shape, place a long ruler against the bottom of the roll and pull the bottom sheet of paper away from you while pushing the ruler inward to snuggly compress the roll. Secure the paper ends with clips, slide the roll into the refrigerator, and let it chill for at least 2 to 3 hours to set.
• Serving
• When ready to serve, unwrap the roll. Dip a sharp chef’s knife into hot water, wipe it dry, and slice the roll into beautiful, even pieces (about 2cm wide). Wipe the knife clean and re-warm it between each slice for perfectly clean, professional edges.