Melt the butter and dark chocolate together in a heatproof bowl set over a pan of simmering water, ensuring the bowl doesn’t touch the water, or in the microwave in 30-second bursts until smooth. Leave to cool for a few minutes. Line a 20cm square (or other cake tin that fits in the air fryer) with baking parchment.

Heat the air fryer to 180C. Tear the hot cross bun into small chunks then tip into the air fryer basket and cook for 3-4 mins until crunchy and golden. Tip into a bowl and lower the air fryer temperature to 160C.

Whisk together the eggs, sugar and a pinch of salt in a large bowl using electric beaters until thick and creamy. Sift over the flour and cocoa powder, then pour in the melted chocolate mixture. Using a spatula gently fold until evenly mixed, then stir in the hot cross buns, chopped chocolate and marzipan, if using.

Pour into the prepared tin and air fry for 25-30 mins until set but with a gentle wobble in the centre. Leave to cool completely before cutting into 9 or 12 rectangles.