Preheat your oven to 350°F (175°C) and grease and flour five 6-inch cake pans; alternatively, line them with parchment paper.

In a medium bowl, whisk together the flour, baking powder, and salt.

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.

Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next, then stir in the vanilla extract.

Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the dry ingredients.

Divide the batter evenly among the prepared cake pans and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean; then let the cakes cool in the pans for 10 minutes before inverting them onto a wire rack to cool completely.

In a large bowl, beat the softened butter until creamy; then gradually add the powdered sugar, mixing until well combined.

Beat in the Biscoff cookie butter, heavy cream, and vanilla extract until the buttercream is smooth and fluffy.

Level the cooled cake layers with a serrated knife if necessary.

Place one cake layer on a serving platter and spread a layer of Biscoff buttercream over it.

Sprinkle a generous amount of crushed Biscoff cookies over the buttercream.

Repeat layers with the remaining cake, buttercream, and crushed cookies, then apply a thin crumb coat of buttercream to the entire cake and chill it in the refrigerator for 15-20 minutes.

Apply the remaining buttercream to the cake, smoothing it with an offset spatula or bench scraper.

Warm the Biscoff spread slightly until pourable, then drizzle it over the top edge of the cake, allowing it to drip down the sides.

Garnish the top of the cake with additional Biscoff cookies, either whole or crushed, for decoration.