Line a baking tray with baking parchment and use one of the mugs you'll use for the cakes as a template to draw two circles on the parchment. Flip the parchment over so the pencil marks are on the bottom. Melt 25g of the dark chocolate in a heatproof bowl in the microwave in 20-second bursts. Or, do this over a pan of simmering water. Spoon the melted chocolate into the middle of the circles and spread out to the inside edge of the templates – you want the chocolate discs to be able to sit just inside the mugs. Sprinkle over the hazelnuts and leave to set.

Spoon 70g of the butter into one of the mugs and melt in the microwave, about 30 seconds-1 min. Pour the butter into a bowl, then brush a little of it over the insides of the two mugs. Add the milk, vanilla, cocoa powder, sugar, flour and a large pinch of salt to the bowl with the rest of the butter. Whisk to combine, then divide the batter evenly between the two mugs. Microwave on high for 1 min-1 min 10 seconds, or until set but gooey. Remove from the microwave and leave to cool.

Remove the ice cream from the freezer about 5 mins before serving to soften slightly. For the sauce, tip the cream and milk into a small pan and heat over a medium-low heat until steaming. Remove from the heat. Add the remaining chocolate and butter to the cream mixture and whisk until melted, combined and smooth. Scoop balls of ice cream over the brownie cakes and top with the frozen raspberries and a chocolate disc. Pour the warm chocolate sauce over the chocolate discs at the table to reveal the ice cream surprise.