Place the water in a a 5-quart bowl, or lidded (not airtight) food container and mix in the yeast, salt, eggs honey, maple syrup and melted butter. Add in the flours, stirring well with a wooden spoon until all of the flour is incorporated.

Cover (not airtight), and allow to sit at room temperature for about two hours.

Place dough in the fridge and chill for at least 3 hours, preferably overnight. Dough is sticky after the initial rise but easy to work with after it is cold. Dough will keep for 5 days in the fridge and up to 2 months in the freezer (freeze after 5 days if you are not going to use it all; divide the dough into 4 equal pieces for easy use).

Make the filling by mixing together the confectioners’ sugar, cocoa powder, chocolate, and butter to form a spreadable paste.

Grease a loaf pan and line bottom with parchment paper.

Remove the dough from the fridge and roll out on a lightly floured surface into a rectangle measuring about 15 by 11 inches. Trim the sides to make them even, then position the dough so that a long side is closest to you. Use an offset spatula to spread the chocolate mixture over the rectangle, leaving a 3⁄4-inch border on all sides.

Use both hands to roll up the rectangle like a roulade, starting from the long side that is closest to you and ending at the other long end. Press to seal the end onto the roulade and then use both hands to even out the roll into a perfect thick cigar. Rest the cigar on its seam.

Trim about 3⁄4 inch off both ends of the roulade with a serrated knife. Now use the knife to gently cut the roll in half lengthwise, starting at the top and finishing at the seam. You are essentially dividing the log into two long even halves, with the layers of dough and filling visible along the length of both halves. With the cut sides facing up, gently press together one end of each half, and then lift the right half over the left half. Repeat this process, but this time lift the left half over the right, to create a simple, two-pronged plait. Gently squeeze together the other ends so that you are left with the two halves, intertwined, showing the filling on top. Carefully lift into a loaf pan. Cover the pan with a wet tea towel and leave to rise in a warm place for 1 hour.

Remove the tea towels, place the loaf on the middle rack of the oven, and bake for about 30 minutes, until a skewer inserted in the center comes out clean.

Remove from oven and leave in pan. Immediately brush the maple syrup over the top. Leave the loaf until it is just warm, then remove from the pan and let cool completely before serving.