For the Ulmer Zuckerbrot mix sugar, flour, yeast, salt, anise and half of the fennel seeds. Add 2/3 of the softened butter, eggs, milk and rum and mix with the dough hook of the mixer until smooth.
Cover and let rise in a warm place until doubled in volume. Knead in the candied lemon peel.
Knead again on floured work surface and roll out to just under 1 cm thick. Cut out 12 cm cookies with a glass. Brush the edges with egg white.
Fold the cookies into small loaves (cut into thirds).
Mix egg yolks with 2 tablespoons water and brush the surface with it. Sprinkle with the remaining fennel seeds.
Place on a baking tray and let rise for 20 minutes. Put in the oven at 200° Celsius and bake the Ulmer Zuckerbrot in 1/2 hour until golden brown.