Heat the oven to 200°C/180°C fan-assisted/Gas Mark 6.
Heat the oil in a large deep frying pan and add the potato, fennel and onion. Cook for 10 minutes until they begin to soften and go golden.
Transfer half of the potato, fennel and onion mixture to a 1½ litre ovenproof dish, and scatter over the tuna then top with the remaining potato mixture.
Mix the chicken stock and half fat crème fraîche and pour over the potato. Scatter with the cheese and transfer to the oven to bake for 25 minutes until golden and tender when pierced with a knife.
Serve with salad or green beans.
Our thanks to the Potato Council for providing this recipe.