In a small saucepan, heat the water, sugar, and honey just until the sugar is melted, but don't let it boil. Set it aside to cool slightly. Finely chop the candied citrus peel.
In the bowl of a stand mixer, combine the flour, chopped peel, ground hazelnuts, cocoa powder, lemon zest, spices, baking soda, baking powder, and salt.
Pour in the warm honey mixture and mix to combine. Add the egg and milk and knead the mixture to a stiff dough.
Form the dough into a ball and wrap in plastic food wrap or pack it into a container and seal it with a lid. Chill the dough overnight or leave it in the fridge for up to 3 or 4 days.
Remove the ball of dough from the fridge and let it come to room temperature for about 30 minutes. Preheat the oven to 350°F (180°C). Grease two cookie sheets or line them with parchment paper.
Cut the dough ball into 8 wedges, and roll each wedge into a ¾-inch (2cm) rope, about 11 inches (28cm) long. Place the ropes onto the cookie sheets and flatten them slightly with your fingers.
Bake for 12 to 14 minutes, until the rolls are puffed but still soft.
While the rolls are baking, stir together the chocolate lemon glaze. Add just enough water, ½ teaspoon at a time, to make a thick but still runny glaze with the consistency of pudding.
Allow the cookie logs to cool for 5 to 8 minutes, then brush the warm logs with the glaze to coat the tops and sides completely. If there's any extra glaze, add a second coat to any thin spots.
Let the logs cool, then cut each one diagonally into about 10 diamond-shaped cookies. When the icing has hardened, store the cookies in an airtight tin with wax paper between the layers. They will keep in a cool place for up to 2 weeks or can be frozen for up to 3 months.
Makes 80 Magenbrot cookies.
Notes
How to toast and grind hazelnuts: Spread the whole, shelled hazelnuts in a single layer in a baking pan, and toast in a 350°F (180°C) oven for 10 to 15 minutes, stirring the nuts halfway through the baking time, until the hazelnuts are golden and you can smell their toasty aroma. Pour the nuts immediately onto a clean tea towel, and gather the towel up around them. Rub the nuts vigorously through the towel to loosen as much of their brown outer skins as possible. Pick the nuts out of the loose skins, let them cool, and then grind them in a food processor, blender (small amounts at a time) or coffee grinder in batches until they're the texture of fine dry bread crumbs. (Don't process them too far, or they will become nut butter. Alternately, if you are toasting hazelnuts that are already ground, spread the ground nuts in a shallow layer in a baking pan and toast them for 8 to 10 minutes, stirring them halfway through, until they turn golden and fragrant.