1. Melt the butter in a large pot gently on a low heat and then add the milk. When the mixture is lukewarm, remove from the heat and add the two sachets of dried yeast, whisking to incorporate.
2. Mix the flour, sugar, salt and cardamom in a large mixing bowl. Make a well and pour the wet ingredients in. Using a wooden spoon mix until you have a rough dough. When the dough has taken shape and is no longer sticky, turn out onto a clean floured surface and knead for about 6 minutes.
3. Dust with a little flour if you find the dough is too sticky. Transfer the dough to a floured bowl, covered by cling film and a towel and let it rise for 45 minutes in a warm dark place.
4. To prepare the filling, in a bowl, beat the butter and sugar together until you have a smooth paste.
5. When the dough has risen, punch it down in the bowl. Roll into a large rectangle about 3mm thick, and then spread the filling all over. In a bowl roughly squash the cranberries and then spread over the dough with the white chocolate. Then, from the long side, roll the dough so you end up with a long cylinder. Slice right down the middle lengthways. Twist each half around each other and join the ends together to form a wreath.
6. Leave to rise again covered for 20 minutes in a warm place. Brush with beaten egg and sprinkle with sugar. Heat the oven to 350˚F
7. When the wreath has risen again bake in the oven for about 20 minutes or until it turns golden brown and is nicely risen. Remove from the oven and allow to cool slightly before slicing and serving.