Bake the gourmet fillet in the oven according to the instructions on the package. Peel and dice the celery and potatoes. Peel and finely dice the garlic cloves. Clean and wash the spring onions and cut into fine rings. Boil the celery cubes with the potato cubes and garlic clove cubes in salted water (1 teaspoon salt) for about 30 minutes, drain through a kitchen sieve, return to the hot pot and sprinkle with butter (1 tbsp), coarse sea salt from the mill (2 big pinches), colored pepper from the mill (2 big pinches) and nutmeg (1 big pinch) work through well with the potato masher. Finally fold in the spring onion rings. Serve the gourmet fillet halved with celery-mashed potatoes and tomatoes.