Mix together the flour, sugar, yeast, and orange zest in the bowl of a stand mixer (or a mixing bowl if you’re making it by hand). Make a well in the centre and add the beaten egg and egg yolk, milk, and salt. Knead with a dough hook for 5 minutes (10 or so minutes by hand), until it comes together in a ball.

Knead in the butter, a dot at a time, until the dough is very soft and smooth. Clean and grease the bowl with butter, then return the dough to it, cover the bowl with cling film or a damp tea towel, and leave the dough to rise for 30 minutes in your kitchen and then overnight in the fridge.

The next morning, prepare the filling. Melt the chocolate and butter together in a bowl set over a pan of simmering water, then take off the heat and mix in the cocoa, icing sugar, poppy seeds, and cinnamon.

Once the filling is ready, grease your work surface with a little butter and roll the cold dough out into a large rectangle, about 40cm long and 30cm wide.

Spread the filling over the dough, right to the edges across the width, but leaving a 2.5-cm wide gap along one of the short edges.

Roll the dough up like a Swiss roll, starting with the opposite short edge and working towards the exposed dough. Pinch the roll closed, then wrap in cling film and transfer to the freezer for 10 minutes, or the fridge for 30 minutes.

Cut it lengthways down the centre, carefully allowing each half to open until they are laying side by side. Twist the two halves over one another two or three times, then lower carefully into the greased loaf tin.

Cover with a damp tea towel and allow to rise for at least 2 hours.

Preheat the oven to 180°C/350°F/gas 4 and, once the dough is swelled and soft, bake it for 40 minutes, or until it is browned on top.

When it has 10 minutes left in the oven, simmer a couple of tablespoons of water, the orange juice, and the sugar together in a saucepan for a couple of minutes until slightly thickened and syrupy, then paint this over the babka as soon as it comes out of the oven.