INSTRUCTIONS
1.Preheat the oven to 220C/425F/gas mark 7.
2.Arrange the tomatoes at the bottom of a buttered oven-proof dish. Cut the fish into chunks and scatter over the tomatoes. Top with the grated cheeses and chives.
3.Pour over the cream, and cook for 20 minutes, until the gratin is bubbling and golden. Serve with baby potatoes.