Aachener Printen (Molasses Spice Biscuits)
Dissolve baking soda in rum. Mix molasses and brown sugar with 3 tablespoons water and heat until sugar dissolves. Place rock sugar in a plastic bag and crush. Mix crushed rock sugar, flour, orange peel, cinnamon, anise and cloves. Knead together rum mixture, molasses mixture and rock sugar mixture to a smooth dough. Wrap dough in foil and refrigerate overnight.
Preheat oven to 180°C (approximately 350°F).
Roll out dough about 5 mm thick (approximately 1/8 inch thick). Cut dough into rectangular biscuits about 2.5 x 6 cm (approximately 1 x 2 inches). Place dough biscuits spaced slightly apart on a baking sheet lined with parchment paper. Brush biscuits with milk and bake about 15 minutes. Remove biscuits from baking sheet to cool. Glaze or decorate biscuits as desired to serve.