Clean the beans, cook in salted boiling water for 10 minutes, rinse and drain well.
In the meantime, peel the onions and cut into fine strips. Wash the tomatoes, divide the stick into 4 portions. Drain the green peppercorns and roughly chop them.
For the vinaigrette, mix the mustard, 125 ml oil, tarragon vinegar, salt and a pinch of sugar with the cutting stick in a tall, narrow container. Season the vinaigrette with the peppercorns.
Season the beef fillets on both sides with black pepper. Heat the remaining oil in a pan. Fry the fillets on each side for 3 - 4 minutes on high heat, remove, wrap in aluminum foil and let rest for 5 minutes.
In the meantime, fry the tomatoes all around in the same pan and then place them on a plate. Deglaze the roast set in the pan with 3 tablespoons of water and add the meat juice that has leaked out while resting. Pour the gravy through a sieve into the vinaigrette and stir well.
Mix the beans and onions with 3/4 of the vinaigrette, place on 4 plates and sprinkle with a little fleur de sel. Cut the fillets into four slices each and arrange on top of the beans. Place the tomatoes on top, drizzle with the remaining vinaigrette, sprinkle with a little fleur de sel and serve.
The Boss Kitchen editorial staff oversees content review, fact-checking, and recipe verification across the site. Published articles pass through the editorial team before going live, ensuring ingredient lists, techniques, cooking times, and nutritional claims hold up in a home kitchen. The team coordinates contributions across the site writers, handles reader corrections, and maintains consistency in measurement conventions, safety guidance, and dietary labeling. Posts under this byline typically represent team-reviewed reference material, site announcements, or editorial roundups rather than individual-author features, and they are held to the same sourcing standards as bylined recipe and product coverage.