Finely chop the leek and sunflower seeds. Chop the meat into bite-sized bites and fry in the hot clarified butter, season and remove. Briefly toast the chopped ingredients in the roasting set, deglaze with cream and bouillon, add a dash of white wine if necessary. Bring to the boil and season with lemon zest, salt and pepper. Put the meat back in and let it get hot for a moment.