Instructions
Follow the steps and taste along the way.
Prepare the cabbage and meat
Thinly slice the cabbage, finely chop the onion, and cut the apple into small cubes. Pat the tenderloin dry and cut it into four medallions of roughly equal thickness. Divide the salt: 2 g for the cabbage, 1 g for the buckwheat, and 2 g for the meat.
Braise the apple cabbage
Heat 20 ml of oil in a pot and cook the onion for 3 minutes, until softened and beginning to turn lightly golden. Add the cabbage and apple, stir, and cook for another 3 minutes. Pour in the apple cider vinegar and 250 ml of water, season with 2 g of salt, cover, and braise over low heat for 20 to 25 minutes. Stir occasionally; the cabbage should soften but not become mushy.
Cook the buckwheat
Toast the buckwheat groats in a small pot without oil for 2 minutes, until fragrant. Add 480 ml of water and 1 g of salt, then bring to a boil. Cover, reduce the heat to very low, and cook for 12 minutes. Remove from the heat and leave covered for another 5 minutes.
Sear the tenderloin
Season the medallions with the remaining 2 g of salt and half of the black pepper. Heat the remaining 10 ml of oil in a large pan. Sear the meat over medium-high to high heat for about 3 minutes per side, until a brown crust forms. If the medallions are thicker, cook them briefly for a little longer; they should reach about 63 to 65 °C in the center. Transfer them to a plate and let them rest for 3 minutes.
Finish the sauce and serve
Add the finely chopped garlic and the remaining black pepper to the same pan; stir for 20 seconds. Pour in the stock, scrape up the browned bits with a wooden spoon, and simmer gently for 3 to 4 minutes to reduce the liquid slightly. Stir in the mustard and thyme, then add the juices released by the meat. Serve the medallions with the buckwheat and cabbage, spooning the sauce over the meat. The cabbage should taste sweet and sour, and the dish should be hot when served.
