1-First Step: Prepare the base: Preheat your oven to 160°C fan (180°C conventional, 350°F, Gas Mark 4). Line an 8-inch square baking pan with greased parchment paper. For the shortbread base, cream together softened butter, Biscoff spread, and brown sugar until smooth. Add vanilla extract and mix well. Fold in the plain flour until combined. Press the mixture evenly into the pan and bake for 20–25 minutes until lightly golden. Let the base cool completely before the next step.

2-Second Step: Make the caramel layer: In a heavy-bottomed saucepan set over low heat, combine the unsalted butter, granulated sugar, golden syrup (if using), and sweetened condensed milk. Stir continuously until the sugar dissolves and the mixture is fully combined. Bring the mixture to a gentle boil, then reduce heat and simmer, stirring constantly for 5 to 7 minutes (or 10 to 12 minutes with induction cookers), until thickened and golden. Do not overcook to keep a soft, gooey caramel. Remove from heat and stir in vanilla extract, optional Biscoff spread, and a pinch of sea salt. Pour the caramel evenly over the cooled base and refrigerate until firmly set this usually takes at least 2 hours.

3-Third Step: Prepare the chocolate topping: Melt the white or milk chocolate in short bursts in the microwave or over a double boiler, stirring often to avoid burning. Pour the melted chocolate over the set caramel layer and spread evenly using a spatula. Tap the pan lightly to remove air bubbles.

4-Fourth Step: Add the Biscoff swirl and decoration: Warm the remaining Biscoff spread slightly until runny, then drizzle over the chocolate layer. Use a cocktail stick or a knife to swirl it into the chocolate, creating an attractive marbled effect. Place whole Biscoff biscuits on top as decoration if desired.

5-Final Step: Set and serve: Allow the traybake to set fully at room temperature or in the fridge before slicing into neat squares. For cleaner cuts, warm the knife blade between slices and consider scoring the chocolate layer beforehand. Serve chilled or at room temperature for the best texture and flavor experience.