Tahini Mississippi Mud Pie

Crush the bourbon biscuits into fine crumbs using a food processor or by placing them in a bag and bashing them with a rolling pin. Mix the crumbs with the melted butter until well combined. Press the mixture firmly into the base and up the sides of a 26cm fluted tart tin, ensuring there are no gaps. Chill in the fridge for at least 30 minutes.

Preheat your oven to 180°C (160°C fan/gas 4). Melt the dark chocolate and 125g of unsalted butter together in the microwave in 30-second bursts, or over a double boiler, until smooth. In a separate large bowl, use an electric whisk to beat the light brown sugar and eggs for 4-5 minutes until the mixture is thick, pale, and creamy.

Gently pour the melted chocolate mixture and 100g of tahini into the egg and sugar mixture. Sift the flour, cocoa powder, and 1/2 tsp salt over the top. Using a large metal spoon, gently fold everything together, taking care not to deflate the air. Pour the batter into the chilled biscuit case and bake on a tray in the middle of the oven for 20 minutes. It should be set at the edges but still have a slight wobble in the center. Cool completely at room temperature for 2 hours.

To make the chocolate custard topping, combine the vanilla custard and additional dark chocolate (if using extra) in a small saucepan. Heat gently over medium heat, stirring constantly until the chocolate has melted and the sauce is smooth. Remove from the heat and allow to cool slightly.