Preheat your oven to 400°F (200°C).

If not already cooked, poach or steam your fish until it flakes easily with a fork. Let it cool, then flake it into bite-sized pieces.

In a large bowl, combine the flaked fish, mashed potatoes, breadcrumbs, chopped parsley, lemon juice, and egg. Add salt and pepper to taste and mix until everything is well combined but not over-mixed.

Using your hands, form the mixture into patty shapes, approximately ½ inch thick.

Lightly grease a baking sheet with olive oil.

Arrange the fish cakes on the baking sheet, leaving space between each one. Brush the tops lightly with olive oil for extra crispiness.

Bake in the preheated oven for about 25 minutes or until golden brown.

Let them cool for a few minutes before serving.