1. Use a potato peeper to remove the peel from the grapefruits down to the flesh. With a knife, remove the grapefruit segments between the membranes, keeping them as whole as possible. Save the juice in a bowl.
2. In a large skillet, saute the kip filets in hot oil until brown, about 5 minutes. Meanwhile, peel and chop the shallots.
3. Salt and pepper the kip filets. Remove them from the pan and keep warm. In the same pan, saute the shallot until translucent. Stir in about quarter cup of the reserved grapefruit juice and the creme fraiche; let the sauce come to a boil.
4. Stir in the cornstarch and cook till the sauce slightly thickens. Add the coriander plus salt and pepper to taste. Add the grapefruit slices to the sauce and warm gently.
5. Cut the kip filets into crosswise slices. Arrange each kip filet on a plate, with grapefruit segments between the slices. Pour the sauce over.
Good with rice.