Preheat the oven to 180°C (350°F) and grease a 12 piece muffin pan and line each with a strip of baking paper with the end of each side of the baking paper hanging out the top of each muffin hole.
Beat the super soft or partially melted butter, brown sugar and sugar together.
Beat in the egg and vanilla extract.
Mix in the flour, baking powder and chocolate chips.
Place two tablespoons of cookie dough into the base of each muffin case and press into a flat layer. Top up each one with any remaining cookie dough.
Melt the butter and chocolate together.
Beat the egg, sugar and vanilla extract until light and fluffy.
Mix the chocolate mixture through the eggs.
Mix in the cocoa, followed by the flour.
Pour the brownie batter over each of the cookie bases and spread evenly
Place in the oven and bake for 20-30 minutes depending on your oven and how cooked you want them. Check them at 20 and if they have loose crumbs attached to a skewer inserted in the middle they are done and will be fudgy. If you want them softer and fluffier, allow them to cook for a further five minutes.
Allow the brookies to cool for ten minutes before using the baking paper 'handles' to lift them out and enjoying warm or allowing them to cool on a rack.