Soak the anchovy fillets in 2 or 3 changes of cold water for 2 hours to freshen. Stem and wash the mushrooms under running water, wipe, keep whole if small, halve or quarter according to size. Heat the oil in a high-sided frying pan, put in the mushrooms to fry for 5 minutes, then pepper. Add the freshened anchovies, mint leaves and lemon juice. Cook to reduce. Serve immediately with an omelet or scrambled eggs, sprinkled with chopped parsley.