Thanks Jamie Oliver for this recipe, which doesn't include a white sauce, you just grate the veg into the dish - simple and use less pots! I added a puff pastry top to impress our dinner guest. He had 3 helpings.

1kg potatoes
1 carrot
2 sticks celery
150g Cheddar cheese
1 lemon
1/2 fresh chili
handful fresh parsley
300g smoked fish (I used terakihi, Jamie used salmon and haddock)
125g king prawns (optional, I didn't have any)
olive oil
salt and pepper
chopped spinach, optional
couple of ripe tomatoes, optional
Frances's extra - pre-rolled puff pastry sheet, optional

Preheat oven to 200C. Bring large pot of water to boil. Scrub potatoes, cut into 2cm chunks and put into boiling water, cook for about 12 min.
In a deep baking tray or earthenware dish grate carrot, celery and cheese and zest of lemon. Add chopped chili and parsley. Add bite size chunks of smoked fish to tray, squeeze over lemon juice, drizzle with oil and season with salt and pepper.
Add the other veges if you have them/want to. Mix ingreds in dish really well.
By now your potatoes should be cooked so mash until smooth with bit of oil and season. Spread over fish mix.
Lay over puff pastry sheet if you want and cut to shape. Brush with milk or beaten egg.
Bake for 40 min or until heated through and pastry golden.
Serve with tomato sauce, green salad or steamed veg.