Make the Biscoff Buttercream (Mousseline cream)

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
• 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 to add the butter in 3 stages and mix 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 temperature 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 cupcakes

Cupcakes

• Heat oven to 175 C / 347°F (no fan)
• With an Electric hand mixer whip room temperature butter and sugar together until pale and fluffy then whip the egg in. Do not overbeat
• Sift flour, salt, cinnamon and baking powder together, this is the “dry ingredients”, while the room temp milk is your wet ingredient
• Start adding the dry and wet ingredients into the batter in the following 4 steps: wet, dry, wet, dry. With a Rubber spatula fold each time
• Mix vinegar and baking soda together in a small bowl, it will be super bubbly. Immediately fold the mixture into the cupcake batter. This is the secret ingredient to keep the cupcakes moist without the taste of vinegar of course!
• Spoon or pipe the mixture into Cupcake pan till approx. ¾. This batch makes 6 large cupcakes
• Bake for 25 min or until a skewer inserted comes out clean then let them cool on a cooling rack before filling and decorating

Assembling

• Once the cupcakes cooled to room temperature, make a small hole on each of them and fill them with the Biscoff spread
• Pipe frosting on top, then decorate with more Biscoff spread and Biscoff cookies
• Store in the fridge for 2-3 days