Beef Wellington with spinach, ham, and mushroom duxelles

Preparing the meat: Generously season the Chateaubriand with pepper and salt. Heat a knob of butter in a pan and sear the meat on all sides, including the edges. This helps retain the juices when slicing. Rub the cooked meat with mustard. Then let it cool completely. 

Making the duxelle: Finely chop the shallots, garlic, and mushrooms (this can be done in a food processor). Melt butter in a pan and sauté the shallots until translucent. Then add the mushrooms. Cook well until all the moisture has evaporated and the mixture is dry. Season with salt and pepper. Let cool. 

Preparing the spinach: Quickly sauté or blanch the spinach. Then squeeze out the excess water very well (use kitchen paper) and chop finely. Set aside. 

Preparing the ham layer: Place a large piece of cling film on your work surface. Lay the slices of ham on top in a rectangular shape, slightly larger than the meat. Spread the duxelle evenly over the ham and then place the finely chopped spinach on top. 

Wrapping the meat: Place the meat at the beginning of the layer on the foil and roll it up tightly using the foil. Twist it closed firmly and let it rest in the refrigerator for at least 30 minutes (longer is fine, even overnight). 

Wrapping in puff pastry: Roll out the puff pastry (cold temperature is important!). Remove the meat from the foil and place it on the pastry. Roll it up tightly and fold the sides underneath. Place on a baking sheet lined with parchment paper, seam side down. 

Finishing: Mix the egg yolk with a splash of milk or water and brush it over the pastry. Cut a pattern into an extra sheet of puff pastry and place it decoratively on top. Brush again with the egg wash. 

Baking: Preheat the oven to 185°C. Preferably use a meat thermometer: cook until the internal temperature reaches 45°C for rare. Expect about 30–40 minutes of baking time. 

Serving: Let the meat rest for 10 minutes before slicing.