Method

• 1.
  Spread the shortbread on a tray, sprinkle evenly with 1 tbs whisky and set aside to dry out. Grease a 20cm x 30cm slice pan and line with baking paper.
• 2.
  Combine both chocolates (reserving extra 100g dark chocolate) in a heatproof bowl over a saucepan of just-simmering water (don’t let base of bowl touch the water), stirring occasionally until just melted.
• 3.
  Meanwhile, combine condensed milk, butter, glucose and remaining 50ml whisky in a medium saucepan over low heat, stirring occasionally until melted and smooth (mixture should be about the same temperature as the melted chocolate). Cool slightly, if needed, before combining.
• 4.
  Add the condensed milk mixture to the melted chocolate in three batches, stirring each to incorporate before adding the next – don’t worry if the mixture starts to look split, it will come together. Add 1 tsp salt flakes, then beat the mixture vigorously with a wooden spoon for about 5 minutes – the mixture will look oily to begin with, but will come together in a beautiful glossy, almost elastic texture. Beat for another 1 minute to thicken.
• 5.
  Spread one-third of the fudge into the prepared tin. Scatter with one-third of the shortbread and one-third of the extra chocolate and some extra salt flakes, if you like. Repeat layers twice more. Refrigerate overnight to firm up.
• 6.
  Before serving, place fudge in the freezer for 30 minutes to make it easier to cut, then remove from pan and cut into pieces with a hot, wet knife. Store in an airtight container in the fridge for up to 2 weeks.