| Preparation | Cooking | Start to finish | 
|---|---|---|
| 25 min. | 35 min. | 60 min. | 
| 1 | Poach 800 g  Fish in 1 litre    fish fumet (or, at a push, just use salted water with 1  bouquet garni) at a gentle simmer until just cooked. To ensure the fish is perfectly cooked, stick an electronic thermometer into the fish and cook until the temperature reaches 140°F (60°C).  | ![]()  | 
| 2 | Take the fish out of the cooking liquid, remove the skin and any bones, then flake (break up) the flesh. Set aside.  | ![]()  | 
| 3 | Prepare and slice 2 onions finely (a mandolin is the ideal tool for this). | ![]()  | 
| 4 | Pour 3 tablespoons olive oil into a saucepan on medium heat. When hot, add the sliced onions. | ![]()  | 
| 5 | Salt and pepper, then cook for about 5 minutes - the onions don't need to brown. Set aside. Preheat the oven to 360°F (180°C).  | ![]()  | 
| 6 | Peel 800 g cooked potatoeses (I'm using rattes here). | ![]()  | 
| 7 | Cut the potatoes into small pieces, then mash coarsly with a fork. | ![]()  | 
| 8 | Add the fish, onions, thyme, salt and pepper, and mix well. | ![]()  | 
| 9 | Fill individual ramekins or a large gratin dish. Top with grated cheese.  | ![]()  | 
| 10 | Bake for 20 minutes, just until the cheese on the top has melted and is nicely browned. Finish browning under the grill if necessary. | ![]()  | 
