Poppy seed or sesame seed -(optional) * (Water which peeled potatos have cooked in. Plain water may be used, but it's not as good.) Sift together dry ingredients. Soften yeast in one third of potato water. Add to flour. Add oil to remaining potato water and stir into the flour mixture. Add eggs and stir briskly to form a ball of dough. Knead on a lightly floured board for 10 minutes. (This MUST be a firm dough) Add more flour if necessary. Return to the bowl--smooth side up. Cover with a towel (tea etc) and let rise at room temperature until the dough rises to the top of the bowl. Knead again on a lightly floured board until smooth and elastic (as for rolls). Pinch off pieces of dough and roll between the palms of the hands to form ropes about 15 cm long and 2 cm wide. Pinch the ends together firmly to make a doughnut shape. Add sugar to boiling water. Drop bagels into water one at a time. As they come to the surface, turn them over. Boil 1 minute longer on the second side. Place on a greased cookie sheet and bake at 230ºC . until the crust is golden brown and crisp--10 to 15 minutes. Bagels may be sprinkled with poppy seed or sesame seed before baking if you like.