1. Add flour, cornstarch, cocoa, sugar into a microwave-safe bowl and mix. Pour milk onto the flour mix, little by little, and mix well until smooth. Add chocolate. Heat it in a microwave on 600W for about 1.5 mins. Remove once. Mix, add butter and mix again until melt completely. Put the bowl in the microwave again for about 1.5 min. Remove from the heat and mix. Let cool to room temperature.
2. Spread the chocolate dough onto the saran wrap and roll it out thinly (About 5mm thick should do it / 25cm x 20cm rectangle). Store in the fridge while you prepare the bread dough.
3. Add all bread ingredients in the pan of your bread machine (as per manufacturer instructions). Select dough cycle and press start.
4. When the dough cycle is complete, remove it from the machine (we want the primary fermentation to be finished).
5. Place the dough on a lightly floured work surface and punch out the gas produced.
Putting it together
6. Roll out the dough into a rectangle (about 30cm x 35cm) on a lightly floured work surface. Place the chocolate sheet on top of the bread dough. Fold the bread dough to cover the chocolate sheet. The chocolate sheet should be covered completely by the bread dough.
7. Roll out the dough again into a rectangle, using a rolling pin, and then fold in 3 lengthwise. Turn the dough 90 degree and repeat the same for a few more times. Finally roll into a rectangle (about 30cm x 20cm) and then roll it into a log shape to slice.
8. Cut in 2 to 3cm thick slices and place each of them on a baking sheet lined with parchment or a baking mat. Do this with all the dough, leaving some space between the log. This will provide the necessary space for the bread to rise.
9. Cover and allow to rise in a warm place until doubled in size, about 40 min.
10. Pre-heat the oven to 180°C. Bake for about 12 to 15 mins. Remove from the oven and let it cool down.