For the leek-spring onion sauce, finely chop boiled egg. Cut leek (as thin as possible) and spring onion into fine rings.
Mix sour cream, a little oil, egg, a little mustard and sugar until creamy, season with salt and pepper.
Mix the cream sauce with the leek and spring onion rings and season with curry and Worcester sauce.
Serve the leek-spring onion sauce with the meat.