Pre-heat your oven to 170℃/340℉/Gas Mark 4.
Line your 9" cake tin with parchment paper.
Put the biscoff biscuits into a food processor and blitz until the cookies look like fine breadcrumbs.
Pour the biscuit crumbs into a bowl.
Measure out the milk and pour the milk into the crumbs. Mix until everything is fully combined.
Pour the mixture into the cake tin and cook in the oven for 15 - 20 minutes. Or until a cake tester comes out clean from the middle.
Leave the cake to cool. Once it has cooled, you now need to add the topping.
In a microwavable bowl, add the biscoff spread and melt it in the microwave until it becomes a liquid, rather than a spread.
Pour the biscoff spread over the top of the cake. Using a silicone spatula, spread the topping to the edge of the cake. Sprinkle over the crushed biscoff all over the top of the cake.
Leave in the fridge to set for a minimum of 2 hours. Once the topping has set, remove it from the cake tin, cut a slice and enjoy.