Cut the sea bass: Pull the pin bones (if any) from the fish with tweezers. Use a sharp knife to remove the skin and cut the flesh into 1-inch cubes.

Slice the potatoes: Wash and scrub potatoes carefully to remove dirt. Peel the skin with a peeler. Start at the root and cut the potatoes into 1/8 inch thick slices.

Mince the garlic: Cut off the root of the cloves and bash them with your knife to peel the skin. Use your knife or a mincer to mince the garlic.

Slice the onion: Half the onion through the middle then slice off the root and head. Make 1/8-inch slices across the onion halves.

Grate the cheese: Place or hold the grater firmly and press the cheese block against the surface. Push downwards to grate the cheddar cheese.

Chop the parsley: Bunch the parsley into a small mound on the cutting board and chop finely with your knife.

Caramelize garlic: Put a pan on medium heat until hot. Add 1 tbsp unsalted butter and 1 tbsp garlic. Stir for 30 seconds to caramelize.

Incorporate the onion: Add 4 oz onion and stir for 2 minutes.

Cook the fish: Add 24 oz sea bass and stir for 3 minutes.

Season the fish: Season the fish with 1 tsp paprika, 1/2 tsp salt, 1/2 tsp pepper, 1 tsp mustard, and 1/2 tbsp all-purpose flour.

Stir in the liquid: Add 1/2 cup water, 1 cup milk, and 3 tbsp heavy cream, and bring it to a boil. Mix until combined for 2 minutes.

Add the potatoes: Turn off the heat. Add 30 oz potatoes and mix well.

Assemble the casserole: Add the mixture to a baking tray. Stack the potato slices overlapping each other to make a fish scale surface. Cover with aluminum foil.

Bake the casserole: Preheat the oven to 425 °F. Bake for 15 minutes then remove the foil. Bake for another 45 minutes.

Add the cheese: Take the casserole out of the oven. Sprinkle 1 oz cheddar cheese on top.

Melt the cheese: Bake at 475 °F for 5 minutes.

Garnish and serve: Remove from the oven and sprinkle 2 tbsp parsley on top. Let the casserole rest, cut into portions, and enjoy.