boil 2 great potatoes in salted water until a not completed cooking (they will be cooking again in the oven)
pre-heat the oven at 428 F (220 C°) then coat a baking pan with oven foil, oil with a little of olive oil and put the aromas
eviscerate and rinse the fish, dry it. Peel and slice the potatoes, lay the potatoes on the bottom, salt and oil again
put the fish on the potatoes and sprinkle (sfumare) with the Cognac
After about 15 minutes, depending from the oven, open the foil and remove a little of the skin for verifying if cooked: the meat shall be well detached from the bones