Preheat your oven to 180°C (350°F). Crush the digestive biscuits in a food processor until fine, then mix them with melted butter in a large bowl until combined. Press this mixture firmly into the bottom of a lined 9x9 inch baking tray to form an even layer. Chill in the refrigerator for about 30 minutes to set.

In a saucepan over low heat, gently combine the condensed milk and Biscoff spread. Stir continuously for about 5-7 minutes until the mixture is smooth and slightly thickened; it should have a glossy finish. Once ready, pour the caramel mixture evenly over your chilled biscuit base, smoothing the top. Allow this to chill in the fridge for another 30 minutes, letting it set before moving to the next step.

While the caramel is chilling, melt your dark chocolate in a heatproof bowl over simmering water or in the microwave in short bursts (about 30 seconds at a time). Once fully melted, remove it from the heat and let it cool slightly before pouring it over the caramel layer. Smooth the chocolate with a spatula for an even finish, then return the tray to the fridge to set for at least 1 hour.

After the chocolate topping has fully set, take the tray out of the fridge and sprinkle crushed Biscoff cookies liberally over the top. This adds a delightful crunch and enhances the Biscoff flavor. Gently press the crumbs into the chocolate layer for better adhesion. Return the tray to the fridge once more to ensure everything is well combined and cool.

When ready to serve, remove the Biscoff Millionaires Traybake from the fridge. Use a sharp knife to slice it into squares or rectangles, wiping the knife in warm water between cuts for a cleaner finish. Arrange these delicious bites on a plate or keep them in the tray for a beautiful presentation. Enjoy with coffee or tea, making it a special treat for any occasion.