Prepare the Brownie Batter: In a medium mixing bowl, whisk together the melted butter and caster sugar until well combined and the mixture starts to look slightly glossy. This ensures an even sweetness.

Add Wet Brownie Ingredients: Beat in the two large eggs one at a time, incorporating each fully until the mixture is smooth and lightens slightly in colour. Stir in the vanilla extract until its fragrant aroma fills the air.

Combine Dry Brownie Ingredients: Sift the plain flour, cocoa powder, baking powder, and salt into the wet ingredients. Fold gently with a spatula until just combined – be careful not to overmix, as this can lead to a tough brownie. Stir in the dark chocolate chips until they are evenly distributed, forming a thick, chocolatey batter.

Prepare the Biscuit Dough: In a separate bowl, cream together the softened butter, light brown sugar, and caster sugar using a stand mixer or hand mixer until the mixture is light and fluffy, resembling pale clouds. Beat in the egg yolk and vanilla extract until fully incorporated and the mixture smells sweet and inviting.

Combine Dry Biscuit Ingredients: Gradually add the plain flour, bicarbonate of soda, and salt to the butter mixture, mixing on low speed until a soft, pliable dough forms. Fold in the milk chocolate chips by hand until they are evenly distributed throughout the dough, creating a classic biscuit dough texture.

Assemble the Brookies: Grease your four ramekins lightly. Divide the brownie batter evenly among the ramekins, spreading it out to form the bottom layer. It should look dark and rich. Then, divide the biscuit dough into four equal portions. Flatten each portion into a disc and carefully place it on top of the brownie batter in each ramekin, gently pressing down to cover the brownie layer.

Air Fry the Brookies: Preheat your air fryer to 160°C (320°F) for about 3-4 minutes. Carefully place two ramekins into the air fryer basket, ensuring they are not touching for even cooking. Air fry for 12-15 minutes. You'll know they're done when the biscuit topping is golden brown and the edges of the brownie are set, but the centre still feels soft and yields slightly when gently pressed. There should be a delightful sweet aroma wafting from the air fryer.

Cool and Serve: Carefully remove the hot ramekins from the air fryer (they will be very hot!) and let them cool on a wire rack for 5-10 minutes. This resting time is crucial for the gooey centre to set slightly and prevent it from being too runny. Serve warm, perhaps with a scoop of vanilla ice cream or a drizzle of caramel sauce.