Preheat your oven to 175 °C (350 °F) and line a baking tray with baking paper.

In a mixing bowl, combine the melted butter, brown sugar, and granulated sugar until smooth and creamy.

Add the egg and vanilla extract, mixing until well combined and glossy.

In a separate bowl, whisk together the plain flour, cornflour, baking powder, baking soda, and salt until aerated.

Gradually stir the dry mixture into the wet mixture until a soft dough forms.

Shape the dough into large balls (about ¼ cup each) and place them on the prepared baking tray.

Gently flatten each dough ball slightly for even baking.

Bake for 10-12 minutes, ensuring the edges set but centers remain soft.

Cool the cookies on the tray for 5-7 minutes before transferring them to a wire rack.

Combine icing sugar with cream cheese or butter until smooth and spreadable.

Spread icing generously on cooled cookies.

Serve and enjoy your Crumbl-Style Cookies warm or store for later.