Method

• Place an empty bowl in the freezer. You’ll need this to cool the custard.
• To prepare the custard, heat the milk with the lemon zest and vanilla in a small pan and slowly bring to the boil. Switch off just as it starts to boil.
• In a separate pan, whisk the yolks, sugar and cornflour until creamy. Slowly pour in the boiling milk, through a sieve (to remove the lemon zest) while stirring with the whisk. Place the pan over a low-medium heat and continue stirring with the whisk until the cream thickens to a custard consistency.
• You need to cool the custard quickly by pouring it into the cold bowl from the freezer. Continue stirring with the whisk for a minute or two, cover with cling film and refrigerate for at least 30 minutes or until ready to use.
• Add the 4 tsp sugar to the espresso (you can make them in one 240ml quantity) and refrigerate until ready to assemble.
• Not more than 2 hours before serving, divide the espresso into four tea/cappuccino size cups. Ideally the cups should be wide enough to hold a digestive biscuit horizontally across the cup just above the coffee without touching it, so the cup supports it. Pipe or spoon custard over each biscuit and top with raspberries and a few mint leaves if required.
• Refrigerate until ready to serve. When eating the dessert, the fun part is cracking through the biscuit so it falls into the coffee.