To make the dough, combine the flour, sugar, milk, egg, dried yeast and salt in the bowl of a stand mixer fitted with the dough hook. Mix on low speed for 5 minutes. Scrape down the side of the bowl and use your hands to bring the dough together, ensuring you reach the bottom of the bowl. Check to see if it is too dry or too wet at this stage; it should be slightly sticky to touch.
Mix for another 5 minutes on medium speed. With the mixer still running, add the butter in two to three stages so it distributes evenly, and mix for 5 minutes until you have a smooth, shiny dough that stretches. Use the window pane test to check the dough: take a small ball of dough and gently stretch it between your hands – you should be able to stretch it very thin without it breaking. If you find that it breaks easily, mix for a few more minutes to continue working the gluten in the flour, then test it again.
Cover the dough with a damp tea towel (dish towel) and rest at room temperature for 45 minutes. Knead the dough on the bench for 1 minute and then return it to the bowl and cover with a damp tea towel again. Refrigerate for at least 2 hours, and up to 12. The dough will slowly ferment as it cools, making it easier to work with.
To make the filling, combine the cocoa powder, sugar, vanilla and cream in a medium saucepan. Heat over a low heat, whisking, until well mixed and just under a simmer. Remove from the heat, add the dice butter and whisk to combine. The mixture should be smooth and shiny. Refrigerate until it thickens to a spreadable consistency.
To make the syrup, combine the water and sugar in small saucepan, bring to the boil and then set aside.
When your dough is ready, grease or line two 25 × 10 cm (10 × 4in) loaf tins and divide the dough into two equal pieces. Use a rolling pin to roll out each piece of dough into a rectangle roughly 35 × 30 cm (13¾ × 12 in), with the shortest side parallel to the edge of the bench. Use a spatula to spread half of the chocolate filling over the surface of the dough, leaving a small strip uncovered along the edge furthest from you. This is where you will seal the dough. Sprinkle 50 g (1¾ oz) of chocolate pieces over the filling.
Gently gather the edge closest to you and roll it away from you, like a 115 Swiss roll. Use a pastry brush or wet fingers to brush the uncovered strip at the far edge with water, to seal the roll at the end and stop it from unravelling. Repeat with the other piece of dough and transfer both to a tray lined with baking paper. Cover with a clean, damp tea towel and refrigerate for 15–20 minutes to firm up. This will make it easier to cut.
Take one piece of dough from the fridge and use a sharp knife to cut it in half lengthways. Overlap the strips to make an ‘X’, with the exposed chocolate filling face up, then twist the pieces over each other like the threads on a screw. You should have at least two twists on either side of the original ‘X’. This will create the swirling effect in the baked babka. Place your twist into a tin with the exposed chocolate side up, folding and twisting to fit. Repeat with your second loaf.
Cover the tins with a clean, damp tea towel and leave them in a warm spot to prove for at least 1½ hours. If your kitchen is cool, you can use the oven or an esky as a proofing box by placing a small tray of warm water at the bottom. This creates the humidity and warmth needed. The dough should rise by half. Check that it’s proved by gently poking it with one finger. If the indent remains, it’s ready; if it springs back quickly, it needs more time.
Towards the end of the prove, preheat the oven to 180°C (360˚F). Once ready, place the tins on the top shelf of the oven and bake for 15 minutes before rotating the trays for an even bake. Bake for another 15 minutes, until your babka is golden brown on top. Brush all of the syrup over the top. Leave to cool in the tin for 10 minutes and then transfer to a cooling rack for another 20 minutes before slicing.
