Wash the potatoes and cook in boiling water for about 20 minutes. Celery wash, clean and finely dice. Peel and finely dice onion and garlic. Wash thyme, shake dry and remove leaves from the stalks
Heat oil in a pan and sauté onion, garlic and celery for about 5 minutes. Wash, clean and dice the tomatoes. Add tomatoes, sugar, thyme and Worcestershire sauce to the pan and bring to the boil. Simmer at medium heat for about 10 minutes. Season to taste with salt and pepper
Drain the potatoes, rinse, peel and dice. Heat clarified butter in a pan. Fry the potatoes for about 20 minutes while turning. Season to taste with salt and nutmeg
In the meantime, wash the fish, pat dry and season with salt and pepper. Place in the pan with the tomatoes. Cover and cook over low heat for about 10 minutes. Arrange with potatoes on plates, garnish with thyme