Method

• 1.
  To make the dough, combine the flour, yeast, sugar, 1/2 tsp fine salt and orange zest in the bowl of a stand mixer fitted with the dough hook. Combine milk and 2 eggs in a jug. With the motor running, add milk mixture to the flour mixture and knead on low speed for 1-2 minutes, until mixture is evenly combined and a stiff dough forms.
• 2.
  Switch to the paddle attachment and gradually add the butter, about 20g at a time, beating well after each addition on low speed until dough is smooth and very elastic (this will take about 5 minutes). Scrape down side of bowl, cover with plastic wrap and set aside in a warm, draught-free place for 1 hour 30 minutes, or until dough has doubled in volume.
• 3.
  For the chocolate filling, combine all ingredients in a large heatproof jug and microwave on high, in 30-second bursts, stirring after each burst, for 1 minute 30 seconds, or until chocolate has melted. Stir vigorously until well combined, glossy and smooth. Set aside at room temperature to cool.
• 4.
  Grease a 24cm (top) x 22cm (base), 2.5L-capacity fluted ring pan with extra butter. Knock back the dough by punching it in the centre with your fist. Turn onto a lightly floured surface and knead for 1-2 minutes, until smooth and elastic and dough has reduced to its original size.
• 5.
  Use a lightly floured rolling pin to roll dough into a 30cm x 35cm rectangle. Spread dough evenly with the chocolate filling. Starting from the longer end, roll up the dough into a tight roll. (At this point, if the dough is too soft and your kitchen too warm, you can place the log, slightly bent to fit, on a large baking tray lined with baking paper and chill for 20 minutes to firm slightly. This will make cutting and shaping the babka easier). Trim ends of roll. Starting about 2cm from the top end, cut in half, leaving the top end intact. Turn each half so that the cut edges are facing upwards. Twist the two halves together, keeping the cut edges facing upwards. Place in prepared pan, wrapping around the centre tube. Cover with plastic wrap and set aside in a warm, draught-free place for 1 hour 30 minutes, or until well risen.
• 6.
  Preheat oven to 180°C/160°C fan-forced. Brush babka with extra beaten egg, and bake for 45 minutes, or until deep golden and babka sounds hollow when tapped on the top. Stand in the pan for 10 minutes before turning out onto a wire rack to cool.
• 7.
  For the marmalade glaze, place marmalade in a large heatproof jug and microwave on high for 30 seconds. Stir well, then microwave for a further 15 seconds, or until bubbling. Immediately stir through boiling water until well combined. Stand for 3 minutes, stir again, then drizzle over the cooled babka. Set aside for 10 minutes to cool slightly.
• 8.
  Cut babka into wedges to serve.