Preheat the oven to 170°C (fan) or 180°C (conventional).
Crush the Lotus cookies into fine crumbs. Sift the flour, baking powder, and salt together. Add the crushed cookies to the flour mixture and stir.
In a separate bowl, mix sugar, oil, and eggs together. Add the Biscoff cream and Greek yogurt, whisking until smooth.
Pour the wet mixture into the dry ingredients and mix until well combined.
Transfer the batter to a greased or lined 20 x 20 cm baking pan. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Let the cake cool completely before adding the topping.
Heat the cream and add the chopped dark chocolate. Stir until the chocolate is melted and smooth. Let the icing cool slightly.
Spread the chocolate icing over the cooled cake. Briefly warm the Biscoff cream until it becomes pourable, then drizzle it over the chocolate. Use a spoon to create swirls or patterns with the chocolate and Biscoff cream.
Optional: Sprinkle crumbled Lotus cookies on top for extra crunch.