Cut the potatoes into large cubes (3-4cm) and place in a large saucepan. Cover with cold, salted water and bring to a simmer over medium heat. Cook for 10-15 minutes, or until soft.
In a blender/food processor, add the sun-dried tomatoes with oil, tomato paste, pine nuts, grated Parmesan cheese, clove of garlic and olive oil. Blend everything into a smooth (fairly thick) pesto-like paste. Season to taste with salt and pepper.
Drain the potatoes and immediately pour in the hot milk. Crush the potatoes lightly using a fork.
Add the pesto and rocket leaves to the potatoes, add some olive oil and stir through.
Heat a non-stick frying pan with olive oil for the fish. Season the fish on both sides with salt and pepper. Fry the white fish until crispy (start with the skin side down).
