To make the dough, tip the flour into the bowl of a stand mixer along with the cinnamon, if using, 1/2 tsp salt and the sugar and yeast. Mix using the dough hook attachment until fully combined. Mix in the milk, then, on a medium speed, add the eggs one at a time. Mix for 5-8 mins until you have a smooth dough that comes away from the sides of the bowl. Leave the dough in the bowl for 10 mins.

Gradually add the butter, one or two cubes at a time, beating until fully mixed into the dough, scraping down the bowl with a plastic spatula, if needed. Tip the dough into a buttered bowl or round plastic container, and cover and chill overnight until nearly doubled in size. If you want to bake on the same day, leave at room temperature for about 2 hrs until nearly doubled in size, then chill for at least 1 hr – the dough needs to be well chilled for the next step.

Meanwhile, make the filling. Melt the chocolate in a small bowl over a pan of warm water, ensuring the bowl doesn’t touch the water, or in 10-second bursts in the microwave, then leave to cool. In a separate bowl, mix the butter and sugar together, then add the ground almonds. Sift in the cocoa powder and mix in the melted chocolate along with a pinch of sea salt to create a spreadable paste.

Tip the dough onto a lightly floured surface and roll out to a neatish rectangle that’s about 30 x 40cm. With the long edge facing you, spread the filling evenly over the dough using a spatula or palette knife, leaving a thin border around the edge, then scatter over the almonds. Starting with the long edge closest to you, neatly roll the dough away from you into a tight log, just like you would when making cinnamon rolls. If you have space in the fridge, transfer the roll, seam-side down, to a tray and chill for 1 hr (this step isn’t essential, but it helps give neat layers to the finished loaf ).

Butter a 900g loaf tin and line with a strip of baking parchment across the middle of the tin, so it hangs over each end. Use a sharp or serrated knife, cut the log in half lengthways to create two long pieces. Lay the two pieces out so they're parallel, then plait together until you have about 8 twists. Transfer to the loaf tin, tucking the ends under slightly, and fattening up the plait to fit. Cover with a tea towel and leave to rise at room temperature for 2-3 hrs, or until risen by about half.

Heat the oven to 180C/160C fan/gas 4 and bake for 45 mins until dark golden – if you have a digital cooking thermometer, it should read 90C when inserted into the middle.

Make the syrup by boiling the sugar with 4 tbsp water in a small pan until the sugar has dissolved. When the babka comes out of the oven, brush liberally with the syrup, letting it soak in a little before you add more, until it’s all used up. Leave the babka to cool to room temperature. Best eaten on the day its baked, but will keep in an airtight container for two days.