Mix yeast, sugar, salt and warm water. Add flour until dough is soft. Knead for 8-10 minutes. Place in greased bowl and let rise for 30-40 minutes. Punch down. Take pieces of dough and roll between hands to form 9 inch strips. Add sesame seeds, poppy seeds or leave plain. Pinch together to form circle. Place each in the pot of boiling water. When they rise and turn over remove with slotted spoon. Bake on ungreased cookie sheet at 450 degrees for 15 minutes.