Spiced and nutty in flavor, these traditional German Christmas cookies are a form of gingerbread. The best-known are Nürnberger Lebkuchen, which are often presented in ornately decorated tins or boxes. These cookies are the modern descendants of medieval gingerbread, which was typically a combination of spices, honey and dried bread crumbs.
In a medium saucepan, bring honey and molasses to a boil. Remove from heat; stir in brown sugar, egg, lemon juice and zest. In a large bowl, combine flour, baking soda and all spices, and stir in molasses mix, citron and hazelnuts. Cover; chill overnight.
Preheat oven to 350°F (167°C). Line baking sheets with parchment paper. On a floured, hard surface roll out a small amount of chilled dough to ¼-inch (6-mm) thick. If dough is sticky, use more flour. Cut dough in 2-inch (5-cm) rounds; transfer to prepared baking sheets. Bake 10-12 minutes. Meanwhile, make icing by heating sugar and liquids in a small saucepan (do not boil). Remove from heat; stir in confectioners’ sugar. If icing crystallizes, reheat and add water or milk. Transfer cookies to rack and while still hot, brush with icing and decorate with almonds, citron or ginger; or, let cool completely and drizzle with melted chocolate. Store in sealed container.