Fish Baked in Tahini

A recipe from Palestine and Jordan, from the cookbook From the Land of Figs and Olives.
1/2 C cooking oil
2 lbs fish fillets, cut into 2-inch cubes
4 potatoes, peeled and sliced
5 T tahini
1/4 C lemon juice
1/2 small hot pepper, diced finely
3 T cilantro, chopped
2 cloves garlic, crushed
3/4 C water
1 t sage
Salt and pepper to taste
In a frying pan, fry the fish pieces over medium heat for about 10 minutes, turning once. Remove with a slotted spoon and place in a casserole.
In the same frying pan, fry the potato slices until they begin to brown. Remove and place on top of the fish.
Place remaining ingredients in a blender and blend until smooth. Pour over the fish and potatoes and bake at 400 F for 15 minutes.