Beef fillet cooked in one piece with chestnut sauce

Ingredients for 4 servings:

• 700 g beef fillet(s) in one piece, approx. 8 cm high
• 200 g chestnuts, pre-cooked
• 2 onions, red, 1 large, 1 small
• 3 cloves garlic
• 600 ml broth (1/2 vegetable broth 1/2 beef broth)
• 500 ml red wine, dry, velvety, e.g. Hécula 2013 Monastrell
• Fleur de Sel
• 1 tbsp, heaped pepper, black (Malabar pepper) whole
• 3 tbsp, heaped thyme, fresh, dried is also possible, then you need less
• 2 tbsp soy sauce, dark
• 1 tbsp, levelled honey
• some cornstarch
• 2 sprigs rosemary
• 1 ½ tbsp clarified butter for frying
• 2 tbsp butter

Instructions

Working time approx. 50 minutes; Rest time approx. 7 minutes; Cooking/baking time approx. 30 minutes; Total time approx. 1 hour 27 minutes

Remove the beef fillet from the refrigerator and place it on a board to prevent it from getting too cold. Preheat the oven to 175°C fan/gas mark 3. During this time, crush the peppercorns in a mortar, finely dice the large onion, peel the garlic and chop 1.5 cloves (the rest will be used for the sauce), wash the thyme and pick off the leaves, wash the rosemary, set aside the stock, and open the wine. Heat a saucepan (the fillet should fit in one piece) and then heat the clarified butter. Meanwhile, season the beef fillet on all sides with fleur de sel, pepper, and thyme (salt, pepper, and thyme will also be needed for the sauce). Brown the fillet on all sides. Spread about 1 tablespoon of butter in a suitable roasting pan. Cut 1 1/2 cloves of garlic into several pieces and scatter them around the edge. Cut the smaller onion in half and add it to the roasting pan. Place the fillet in the center and add a sprig of rosemary to each side. Cook in a preheated oven at 175°C for 30 minutes, then let it stand with the oven door open for about 7 minutes. After this time, the fillet is medium-rare (still rare). Add the remaining butter to the still-hot pot. Brown the finely chopped onion and chopped garlic (not too dark, otherwise the sauce will become bitter). Briefly fry the precooked chestnuts, some of the ground pepper, fleu de sel, and thyme, then deglaze with the red wine and reduce until almost no liquid remains. Then add the stock (vegetable and beef), honey, and soy sauce and reduce slightly. Mix a little cornstarch with cold water to thicken the sauce. Serve with roasted fennel and roasted diced potatoes. For a more flavorful version, serve with truffled mashed potatoes instead of the diced potatoes.