In a medium saucepan, combine water, sugar, and honey over medium heat. Stir gently until the sugar dissolves, about 3-4 minutes, then remove from heat and let it cool slightly.

In a large mixing bowl, combine flour, mixed candied citrus peel, ground hazelnuts, cocoa powder, lemon zest, German Lebkuchen spice mix, and cinnamon. Sprinkle in the baking soda, baking powder, and sea salt, mixing well.

Slowly pour the warm honey syrup into the dry ingredient mixture while mixing on low speed. Add the egg and milk, kneading until a stiff dough forms, about 5 minutes.

Wrap the dough tightly in plastic wrap and refrigerate for at least 12 hours or up to 5 days.

Preheat your oven to 350°F (180°C) and prepare baking sheets lined with parchment paper.

Divide the chilled dough into 8 equal portions, roll each into a ¾-inch thick rope, and place on prepared baking sheets.

Bake for 12-14 minutes until puffed and slightly soft in the centers. Allow cooling on sheets before transferring to a wire rack.

Mix icing sugar, cocoa powder, and lemon juice in a small bowl. Adjust consistency with water as needed.

Brush warm cookies with the glaze and let it seep in.

Let cookies cool completely before slicing diagonally into diamond shapes and storing in an airtight container.