Bake the cake layers

• Preheat the oven to 175°C and grease and line three 20 cm round cake pans.
• Cream the softened butter with the brown sugar and granulated sugar until light and fluffy.
• Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.
• Whisk together the flour, baking powder, baking soda and salt.
• Add the dry ingredients to the butter mixture alternately with the buttermilk, mixing just until combined.
• Divide the batter evenly between the prepared pans and bake until a toothpick comes out clean.

Make the Biscoff buttercream

• Beat the remaining softened butter until pale and creamy.
• Add the powdered sugar gradually and beat until smooth.
• Mix in the Biscoff cookie butter spread until fully incorporated.
• Add the cold heavy cream a little at a time and whip until light and fluffy.

Fill the cake

• Let the cake layers cool completely, then level the tops.
• Place the first layer on a cake board and spread a layer of Biscoff buttercream, then a swirl of Biscoff spread.
• Repeat with the remaining layers, stacking them evenly.

Crumb coat and chill

• Cover the whole cake with a thin crumb coat of buttercream.
• Smooth the edges with a scraper and refrigerate until the coating is firm.

Decorate and serve

• Cover the chilled cake with a final smooth layer of Biscoff buttercream.
• Pipe decorative borders and swirls of Biscoff spread on top.
• Finish with crushed Biscoff cookies around the base and on top.
• Slice and enjoy.