Briefly rinse the fresh or defrosted sea bream fillets and dry them with kitchen paper. Salt and sprinkle with lemon juice on both sides. Leave on for 10 minutes, then dry again.
If the underside of the asparagus is dry, cut off at least 4 cm from the bottom, otherwise 2 - 3 cm. Test on an asparagus from where you have to peel. Depending on the quality, it is from halfway or just the light green lower part. Peel the asparagus and keep ready wrapped in a damp tea towel.
Clean and chop the mushrooms. Do not wash! Fry a little in the olive oil over a moderate heat. Squeeze the garlic and stew briefly. Sprinkle with the chicken stock and stir in well. Season to taste with pepper and nutmeg. Mix the cream with the marsala and use it to deglaze the mushrooms. Stir in the celery leaves and keep the sauce ready with the lid warm.
Wash the garnish ingredients and use them to prepare the serving dishes.
Flour the gilthead fillets thinly and fry on both sides in moderately hot olive oil. Let as little color as possible get. Remove from the pan, drain a little and divide into the serving bowls.
Fry the asparagus in the remaining olive oil for 2 - 3 minutes, place with the sea bream fillet, spread the mushroom sauce over the fillets and asparagus. Serve warm and enjoy.