Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper and place your chosen fish fillets on it. Dot the fish with butter and sprinkle with rock salt. Bake for about 15-20 minutes, or until the fish is opaque and flakes easily with a fork.

While the fish is baking, heat a large pot over medium heat and add a tablespoon of butter. Sauté finely chopped onions and minced garlic for 3-4 minutes until they become fragrant and translucent.

Stir in diced carrots and potatoes, cooking for an additional 5-7 minutes until the vegetables begin to soften.

Once your carrots and potatoes are tender, mix in a cup of peas and pour in either coconut milk or regular milk. Bring the mixture to a gentle simmer over medium heat. Let it simmer for about 5 minutes to thicken slightly.

After the fish is done baking, remove it from the oven and flake the fish into bite-sized pieces. Gently stir it into the soup. Taste and adjust seasoning if needed.

Ladle the creamy fish and vegetable soup into bowls, garnishing with fresh herbs if desired. Serve hot, accompanied by warm crusty bread or a fresh garden salad.