Chocolate babka

Method

1. Gently warm the milk and 40g of the butter in a small saucepan until the butter has melted – don’t let it boil. Put the flours, salt, sugar and yeast in the bowl of a stand mixer and stir to combine. Make a well in the centre, then pour the warmed milk and one of the beaten eggs into the bowl. Mix with a wooden spoon until just combined, then mix at medium speed with the dough hook for 15 minutes until smooth. The dough will seem wet but will stiffen later when kneaded.
2. Turn the speed up slightly and add the remaining butter, a tablespoon at a time, making sure each addition is incorporated into the dough before adding the next. Mix for 5 minutes until the dough is smooth, slightly sticky and very elastic. Cover the bowl with cling film and leave to rise at room temperature for 45-60 minutes until nearly doubled in size. Chill for another 30 minutes.
3. Meanwhile, make the filling. Put the butter and sugar in a small saucepan and gently heat until melted, then add the remaining ingredients and stir until well combined. Remove from the heat and leave to cool until barely warm. It may look a little grainy because of the sugar but that’s not a problem.
4. Flour your work surface, then tip out the dough and flour that too. Roll out to a 28cm x 60cm rectangle, moving the dough often to prevent it sticking and dusting with extra flour if necessary. Spread the filling over the dough, then take a long edge and roll up tightly like a swiss roll.
5. With the seam underneath, cut the dough lengthways down the centre, leaving the halves attached at one end by about 4cm. Twist the two strands around each other, then lay the dough in the tin, from one end to the other and back in a zig-zag [K]. It doesn’t have to be neat. Cover loosely with cling film and leave in a warm place to prove for about 30 minutes. It’s ready when a gentle prod from your finger leaves a slight indentation in the dough. Heat the oven to 180°C/160°C fan/gas 4.
6. Very gently brush the top of the loaf with the remaining beaten egg, then bake for 1 hour, loosely covering with foil after 25 minutes. Cool in the tin for 10 minutes, then turn out onto a wire rack to cool completely.