How to make a cake with cocoa powder?

Ingredients:
3 large bananas, 6 teaspoons orange juice, 1 teaspoon cocoa powder, 2 teaspoons cornstarch, 3 teaspoons milk, 40g dark chocolate, 15g butter, 175g syrup, 100g plain flour, 1 egg, 1 teaspoon vegetable oil, and oil for the pancakes.
Instructions:
1. Peel and thinly slice the bananas. Place on a plate with the orange juice and set aside.
2. Combine the cocoa powder and cornstarch in a bowl, then stir and add the milk. Chop the dark chocolate into small pieces and add to a frying pan with the butter and syrup. Heat over low heat, stirring until thoroughly combined. Add the cocoa mixture, bring to a simmer, stirring, and simmer for 1 minute. Remove from heat. The chocolate sauce is ready.
3. For the cookie, sift the flour and cocoa powder into a bowl, then add the egg and oil. Gradually whisk in the milk until the mixture forms a smooth paste. Heat a little oil in a heavy-bottomed frying pan. Pour a little batter into the pan. Gently swirl the pan to spread the batter evenly. Cook over medium heat until the bottom is golden brown. Flip the pancake and continue frying on the other side. Remove the pancake from the pan and keep warm. Repeat this process until all the pancakes are cooked.
4. Reheat the chocolate sauce for 1-2 minutes. Place the banana on the pancake, fold it into a triangle, and drizzle with a little chocolate sauce. Serve immediately.