Cozonac (Romanian Christmas and Easter bread)

Method

1. Combine the flour and yeast in a large bowl or stand mixer fitted with a paddle attachment. Add the warmed milk, then mix well. In a separate bowl, crack in 2 of the eggs, then add the yolks of 2 more, reserving the whites (which will be used in the filling). Add the sugar and vanilla extract to the eggs, then beat until foamy. Mix in the soured cream and orange zest. Use a wooden spoon or mixer to incorporate the egg mixture into the flour mixture. Beat (on a medium speed) for 5-8 minutes until thick strands of dough begin to separate. Start adding the butter, 1 tbsp at a time, beating well after each addition. At this stage you can change to a dough hook or knead by hand until the dough is smooth and coming away from the sides of the bowl. Transfer the dough to a bowl greased with sunflower oil, then cover and leave to rise for in a warm place for 1½ hours.
2. Meanwhile, make the filling by whizzing the walnuts and sultanas together in a food processor. Add the milk and orange blossom water, then mix well. In a separate bowl, beat the reserved egg whites with the 75g sugar to stiff peaks, then combine with the walnut mixture. Set aside.
3. Grease and line the loaf tins with sunflower oil and baking paper. Turn out the dough onto a lightly oiled work surface, shape it into a log and divide into 4 equal parts. Gently stretch and roll one part into a rectangle the length of the tin and double its width. Spread with a quarter of the filling mixture, then roll it up into a long log. Repeat with the second piece of dough, then twist these together, tucking in the ends if necessary. Put the dough in the tin. Repeat with the other pieces of dough and put these in the second tin. Cover and leave to prove for 30 minutes in a warm place.
4. Heat the oven to 160°C fan/gas 4. Beat the remaining egg and brush the loaves with it. Bake the breads on the lower shelf of the oven for 20 minutes, then reduce the temperature to 140°C fan/gas 3 and bake for a further 30 minutes until a skewer pushed in comes out clean. Cover the tops with foil if they turn too dark. Leave to cool in the tin, covered with a cloth, for 10 minutes, then remove to a wire rack to cool completely, still covered with a cloth.