This shortbread base is topped with salted caramel, roasted peanuts and homemade peanut butter, and finished with a layer of tempered dark chocolate.
Put the flours, salt and sugar into a processor and pulse to combine. Add the butter and vanilla and blitz to combine to a dough.
Turn out the dough onto a large sheet of baking paper, gently knead it into a ball, then shape it into a brick. Place another sheet of baking paper on top and, using a rolling pin, roll into a 1cm-thick rectangle at least the size of your mould tray. Use a sharp knife and a ruler to cut bar shapes. Press the bars into each hollow in the mould tray. Prick with a fork, then chill for 15 minutes. Heat the oven to 180°C/160°C fan/350°F/Gas 4.
Bake the bars for 14–16 minutes, until golden at the edges. Meanwhile, start making the peanut butter. Tip the peanuts into a baking tray and dry-roast on the oven shelf beneath the shortbread, for 10–12 minutes, until golden, then remove and allow to cool. Take the shortbread out of the oven, place the tray on a wire rack and cool.
Continue making the peanut butter. Put 100g of the roasted peanuts, and the salt, honey and oil in a processor and blitz to a paste. Set aside. Put the reserved peanuts in the processor and chop up.
To make the caramel, slowly heat the cream and vanilla in a small pan until almost boiling. Meanwhile, warm a medium pan over a medium–low heat. Add the glucose and 60g of the sugar and heat gently, swirling the pan, until dissolved and a light straw colour.
Add the remaining sugar and heat for 15–25 minutes, stirring occasionally, until dissolved. Remove from the heat, then add the heated cream. Return the pan to a low heat and stir continuously, until melted and smooth. Remove from the heat.
Stir in the butter, then mix in 2 tablespoons of the peanut butter and the chopped peanuts. Spoon 1 rounded tablespoon of the peanut caramel on top of each shortbread bar (still in the mould tray) and spread evenly. Chill until set.
Melt 165g of the chocolate in a bowl over a pan of simmering water until it reaches 45°C/113°F on a sugar thermometer. Stir in the remaining chocolate to melt. Pour this over the caramel-topped shortbread bars and spread evenly. Chill for about 1 hour, until firm. Pop out of the moulds to serve.