Lightly grease and then line the base and sides of the cake tin with baking paper.
Break the chocolate into pieces and place in a heatproof bowl with the butter. Place over a pan of hot water and stir occasionally until melted.
Place the egg, brown sugar and vanilla extract into a mixing bowl and beat until smooth and creamy (approximately two minutes with a hand mixer, a little longer with a wooden spoon).
Add the melted chocolate mixture, flour, walnuts and milk and mix thoroughly with a wooden spoon.
Preheat the air fryer.
Pour the mixture into the prepared cake tin, place the tin into the frying basket and bake at 170°C for 40-45 minutes.
Leave to cool in the tin for 30 minutes before turning out onto a wire rack to cool completely.
Cut into squares and store in a cake tin.
About this blog
At Morphy Richards, we know lots of people take pride in their homes. That's why we created this blog, a resource for all things home-related and the only place you'll need to visit to get the most out of your products