Set the oven to 400 degrees
Peel the potatoes, cut into small chunks and put on the stove to boil
In a deep baking dish, grate the celery, carrots and cheese using a course grater
Grate the zest from the lemon, finely chop the chile and toss it all into the baking dish
Finely chop the parsley and add to the dish
Cut the fish into bite-sized chunks and add to the dish, together with the shrimp
Squeeze the lemon juice into the dish, and add salt and pepper to taste
Get your clean hands into the dish and mix thoroughly
When mixed, push all ingredients down with a flat hand so it forms a firm base for the mashed potatoes
Drain and mash the potatoes, add the butter and salt & pepper to taste
Scoop out the mashed potatoes into the dish and level-off with the back of a large spoon
Using a fork, score the top of the mashed potatoes so that they brown easier
Place baking dish in the oven and cook for 40 minutes at 400 degrees
When done, leave stand for 10 minutes before serving
