1. Preheat oven to 175C.

2. Grease and line a 30cm ovenproof frypan.

3. Beat the butter, sugars and vanilla in the bowl of an electric mixer until pale and creamy. Add the eggs and yolk, one at a time, scraping down the sides of the bowl between additions to ensure everything is incorporated.

4. Add the flour, cocoa powder, bicarbonate soda and pinch of salt and stir with a wooden spoon until combined.

5. Stir in the chopped white, milk and dark chocolate. Transfer the mixture into the prepared frypan, pressing down – don't worry if it doesn't quite reach the edge, the dough will expand as it cooks. Bake for 20 minutes for a slightly chewy biscuit, but given it's baked in a frypan the cookie will be denser, more cake-like in texture.

6. While the cookie is baking, make the hot fudge sauce. Place the chopped chocolate and cocoa in a heatproof bowl. Combine condensed milk, glucose and ⅓ cup water in a small saucepan. Place the saucepan over medium-high heat and bring to a simmer. Once simmering, remove from heat and immediately pour the milk mixture over the chocolate mixture. Set aside for 5 minutes or until the chocolate has melted, add the peppermint oil (if using), and stir until smooth. Keep warm until ready to serve.

7. To serve, drizzle a little fudge sauce over the cookie, sprinkle with chocolate-mint leaves (if using) and serve with cream or ice-cream.

Note: The cookie dough can be made one day ahead; cover the frypan with clingwrap and store in the fridge. The hot fudge sauce can be made ahead and reheated while the cookie is baking.

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