Persian Rice

Ingredients for 8 Portions:
2 cups basmati rice, rinsed very well
3 quarts water, brought to a boil with 3 tablespoons of salt
2 tablespoons olive or vegetable oil
1 russets potato, peeled, cut into 1/4-inch slices
salt to taste
pinch of ground cumin
5 or 6 slices of butter for top
pinch of saffron, ground and mixed with 1 1/2 tablespoons hot water
parsley to garnish