Put the flour into a large mixing bowl of electric mixer fitted with a dough hook and add the yeast, flour improver and salt. Mix together to combine.

In a small saucepan, heat the milk and 50g of the butter gently until butter is melted and mixture is lukewarm.

Add the milk mix and egg to the dry ingredients and using mixer, knead for 5 minutes until dough is soft and elastic. Cover with cling-film or a tea towel and set aside in a warm place for 1 hour or until doubled in size.

While dough is rising make filling. Soften remaining butter and mix with sugar, syrup and speculaas spice. Grease and line a baking tray with baking paper.

Flour a clean dry bench and roll out the dough into a rectangle about 5mm thick and 25cm wide. Cut into 8 strips and spread over half of the spice mixture. Roll the strips into a spiral and place on the prepared tray. Spread over the remaining spice mixture. Leave to rise for 15minutes while preheating oven to 225°C.

Bake the bolussen in preheated oven for 10-12 minutes. Leave to stand for 5 minutes before transferring to a wire rack to cool completely or serve immediately.