Giant Twix tart

Method

1. Heat the oven to 170°C/fan150°C/ gas 3½. Lightly oil the tart tin. For the base, whizz the shortcake biscuits in a food processor, then pulse in the melted unsalted butter until the mixture has a moist, sandy texture. Line the tart tin by pressing down into the corners so they’re sharp and pressing the crumbs up the side to form even edges. Chill for 10 minutes, then bake in the oven for 15 minutes or until crisp. Leave to cool, then transfer to the fridge.
2. For the caramel, put the 125ml double cream and the condensed milk in a saucepan and heat very gently. Keep warm. Put the golden syrup and caster sugar in a separate heavy-based saucepan with 30ml cold water and heat gently until the sugar melts. Bring to the boil, then simmer for about 5 minutes until a digital thermometer reads 120°C (see Know-how). Remove from the heat and stir in the chopped butter and the cream mixture (take care, it might spit). Return to the heat and bring back to the boil. Cook, stirring, until it reaches 115°C, then pour onto the biscuit base. Leave to cool completely.
3. While the base is cooling, make the chocolate ganache topping. Finely chop the chocolate and put in a heavy-based pan with the 75ml cream and knob of butter. Heat extremely gently, stirring every so often, until the chocolate melts into the cream and the mixture is smooth. Allow to thicken slightly, then pour over the caramel and smooth into gentle peaks using a spoon or palette knife. Transfer to the fridge to chill for 2 hours or until the ganache is firm, or leave overnight.
4. To serve, remove the tart from the tin and let it come up to room temperature for 20 minutes, then slice into fingers.