Make the dough: dissolve the yeast in the lukewarm milk. Add the egg, sugar, cardamom and salt, then the flour little by little. Knead for 5 minutes, add the soft butter in pieces and knead for another 5 to 8 minutes, until the dough is smooth and comes away from the sides of the bowl.

Cover the dough with a tea towel and leave to rise for 1 hour in a warm place, until doubled in size.

Make the filling: mix the soft butter, brown sugar and cinnamon into a smooth paste.

On a floured work surface, roll the dough into a large rectangle of about 40 × 50 cm. Spread the filling over the whole surface, then roll the dough up from the long side into a long, tight log.

Cut the log into trapezoids, alternating the direction of the diagonal cut: one wide side of about 5 cm and one narrow side of about 2 cm. Stand each piece on its wide side, then press down firmly in the centre with both thumbs so the spirals pop out on the sides.

Place the buns on two baking trays lined with baking paper and leave to rise for another 30 minutes under a tea towel. Preheat the oven to 225 °C (fan 210 °C).

Brush the buns with beaten egg, sprinkle with pearl sugar and bake for 10 to 12 minutes, until nicely golden. Leave to cool slightly on a rack before serving.