Prepare a cake stand or serving dish that's at least 8 inches long, ready for your cake to go on.
Add the Biscoff spread to a large bowl then use an electric whisk to whisk in a few tablespoons of the cream. Once that's smooth, add a little more cream. Keep whisking in the cream until it's all used up and the mixture is firm, holding stiff peaks.
Gently fold in the powdered sugar.
Spread some of the cream mixture in a vertical line along your serving dish.
Stick your first batch of 5 biscuits together using the cream then place them upright onto your serving dish. Repeat for the next 9 batches, placing them in a log shape as you go. I made mine 10 biscuits wide and 5 biscuits long.
Use the remaining cream to cover the whole log then place it into the fridge for 6 hours. This will allow the biscuits to soften.
When you're ready to serve your cake, remove it from the fridge and decorate it with melted Biscoff spread, biscuits and sprinkles. Then just cut it into slices and enjoy!