Preheat oven to 180°C (350°F). Line a 6-count muffin tin (½ cup hole capacity) with non-stick muffin liners with high sides- see notes below.

Place the butter and milk into a microwave-safe jug and microwave for 30 – 45 seconds to melt the butter and warm the milk.

Into a mixing bowl, add the okara, cocoa powder, milk, and butter and stir until well combined.

Place the eggs and sugar into another mixing bowl and beat with an electric mixer on high speed for about 3-5 minutes or until the mixture becomes thick and whitish in color.

Add about ⅓ of the egg mixture to the okara mixture and stir with a spatula or wooden spoon until well combined. Then gently fold in the remaining egg mixture until combined.

Pour the mixture into the prepared muffin tin, evenly filling each hole to the top. Bake for 25 - 30 minutes or until a wooden skewer inserted into the center comes out clean.

Remove from the oven and allow the cakes to stand in the tin for 10 minutes before transferring them to a wire rack to cool completely.