Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan to prevent sticking.

In a large mixing bowl, combine the vanilla cake mix, eggs, water, and vegetable oil. Use a hand mixer or whisk to blend until smooth and well combined.

Pour the batter into the prepared baking pan, smoothing the top with a spatula. Bake in the preheated oven for 25-30 minutes or until a toothpick inserted in the center comes out clean.

Allow the cake to cool in the pan for about 10 minutes, then turn it out onto a wire rack to cool completely.

Once cooled, use the handle of a wooden spoon to poke holes all over the top of the cake, about an inch apart.

In a separate bowl, mix the Biscoff spread and sweetened condensed milk until smooth. Pour this mixture evenly over the top of the cake, ensuring it fills the holes.

In another mixing bowl, beat the heavy whipping cream and powdered sugar on medium-high speed until soft peaks form. Spread this whipped cream over the Biscoff layer on the cake.

Crumble Biscoff cookies on top of the whipped cream for a crunchy topping, and sprinkle chocolate shavings or cocoa powder if desired.

Allow the cake to chill in the refrigerator for at least 2 hours before serving.