Make the Biscoff Mousseline cream (German buttercream)

Pastry cream

• In a large enough bowl with the help of a Hand whisk, mix together sugar and egg yolk until slightly fluffy for about 1-2 minutes
• Mix in corn starch and flour until throughly incorporated and have a smooth paste
• Bring milk to simmering in a saucepan on medium heat. Make sure it is simmering but not crazy boiling, see my tips above
• Pour the warm milk over the egg yolk mixture slowly while whisking vigorously with a Hand whisk.
• Pour the mixture back into the saucepan and cook on medium heat for a few minutes until it thickens. Concretely it is approximately 1 min after the first boil. It might get lumpy first, don't worry just keep whisking and the cream will get smooth and glossy
• If in doubt, strain the pastry cream for a lump-free, creamy end result
• Add in room temperature soft butter and mix with a Rubber spatula until completely incorporated. It is worth adding the butter in 3 stages and mixing well after each addition
• Place the cream into a shallow bowl and cover the entire surface with plastic wrap to avoid skin forming on top. Let it cool to room temperature

Make the Biscoff mousseline cream (German buttercream)

• Crème mousseline can be made with room temp pastry cream, room temp butter, and Biscoff spread. Make sure everything is at room temp otherwise the mixture might curdle
• Whip room temp butter first for 1-2 minutes, then mix in Biscoff spread
• Start adding in the room temp pastry cream in 4 stages until cream reaches a stable yet fluffy texture. Do not over whip the mixture as it can become runny
• Place the cream into the fridge for half an hour while preparing the cake layers

Cake layers

• Heat oven to 175 C / 347°F (no fan)
• Cream room temperature butter and sugar together in a stand mixer until pale and fluffy then whip the eggs in, one at a time
• Sift flour, salt, and baking powder together, this is the “dry ingredients” and the room temp milk is your wet ingredient
• Fold wet and dry ingredients with the butter-sugar mixture in the following order: wet, dry, wet, dry.
• Divide the cake batter between the 3 baking pans equally using a digital scale.
• Bake them at 175 C / 347°F (no fan) for 20 min or until a skewer inserted comes out clean. Let them cool on a cooling rack before frosting.

Assembling

• Measure the frosting: 200g Biscoff buttercream and 100g Biscoff spread in between each layer
• Start to build up the layers from the bottom to the top. Once the last cake layer is placed, chill the cake for a minimum of 30 minutes
• If at any point the frosting gets soft or the cake gets unstable, place it into the fridge to chill then only after continue.
• Crumb coat the cake with a thin layer of frosting and then chill the cake again for another 30 minutes before the final coating and decorating

Decoration

• Cover the cake completely on the top and lightly on the sides with the Biscoff crumbs
• Then, move the remainign frosting into a piping bag and decorate top of the Biscoff cake using a star nozzle tip
• Store in the fridge for 2-3 days