Light grease and flour a baking sheet. Cook the potatoes in a pan of boiling water for 10 minutes, or umtil soft. Drain and mash.
Transfer the mashed potatloes to a large mixing bowl. Stir in the yeast, flour, and bouillon, and mix to forn a smooth dough. Add garlic, rosemary, and 3/4 of the cheese and knead the dough for 5 minutes. Make a hollow in the dough, then pour in the oil, add the salt, and knead the dough again.
Cover the dough and leave it to rise in a warm place for 1 1/12 hours, or until doubled in size.
Knead the dough again, and divide it into 3 equal portions. Roll each portion into a sausage about 14 inches/35 cm long.
Press one end of the braids together, then carefully braid the dough, without breaking it, and fold the remaining ends, under, sealing them firmly.
Pllace the braid on the baking sheet, cover and leave to rise for 30 minutes.
Sprinkle the remaining cheese over the top of the loaf. Cook in a preheated oven for 40 minutes of until the bottom of the loaf sounds hollow at 375F/190C.