Fish "en papillotte"

Any white fish is easily prepared "en papillotte". Pull out a sheet of aluminum foil and place the ingredients on it: vegetables like carrots, celery, or spring onion cut in matchsticks ("julienne"), some cherry tomatoes,  olive oil, salt & pepper and a dash of white wine, and then place the fish on top. Close the papillotte by folding up the sheet around the ingredients, and cook in the oven 10-15 minutes. Served here with mashed potatoes in which we let some pecorino cheese melt towards the end.