Stir milk, yeast and half the sugar in a bowl and stand until foamy (10 minutes).
Combine flour and remaining sugar in the bowl of an electric mixer fitted with a dough hook, add eggs, oil, orange-blossom water and yeast mixture and mix until smooth and elastic (5-10 minutes), then, mixing continuously, gradually add softened butter until incorporated. Add glacé orange and aniseed, transfer to a lightly oiled bowl, cover and stand in a warm place until doubled in size (1½-2 hours).
Preheat oven to 200C. Knock back dough, roll out into a rough 30cm x 20cm rectangle, cut slits in bread, gently pull slits slightly open, and set on baking paper in a draught-free place until doubled in size (1 hour).
Bake gibassier until dark golden and cooked through (10-12 minutes). Dust with icing sugar and serve warm.