Separate the egg whites and yolks, placing them in two bowls that are completely clean and free of oil or water. Refrigerate the egg whites for about 10 minutes to help with whipping.

Peel the banana and mash it with 10ml of water until smooth. You'll need about 70g of mashed banana for the dough. Prepare your baking tray by lining it with parchment paper or a silicone mat. Preheat the oven to 120°C (248°F).

Sift the egg yolks into a large bowl. Add the mashed banana and mix with a silicone spatula until combined.

Sift in the cake flour and mix gently until smooth and free of lumps. Avoid overmixing to keep the mixture tender.

Remove the egg whites from the fridge. Add a few drops of lemon juice and begin whipping with an electric mixer on high speed until stiff peaks form.

Add the cornstarch to the whipped egg whites and continue whipping until they are firm and glossy. This will ensure the biscuits are light and crisp.

Take one-third of the whipped egg whites and gently fold it into the banana and egg yolk mixture. Use a "folding" motion, not stirring, to avoid deflating the meringue.

Gradually fold in the remaining whipped egg whites until the batter is smooth and fluffy. Transfer the batter into a piping bag or a ziplock bag with a small cut at the tip.

Pipe the dough onto the prepared baking tray in small, uniform finger shapes (about 5-6cm in length with a 2cm space between each one).

Optionally, sprinkle a small amount of black sesame on top for added flavor and decoration.

Place the baking tray in the preheated oven and bake for 40 minutes at 120°C (248°F), or until the biscuits are golden and crisp to the touch.

Allow the biscuits to cool completely on the tray. Once cooled, they will become even crispier. Store in an airtight container to maintain their crunch.