Step 1

Move the puff pastry to the fridge to thaw.

Step 2

Season each steak with 1 teaspoon of salt and pepper on both sides.

Step 3

Heat 1 tablespoon of olive oil in a pan over high heat until it's hot but not smoking. Sear the steaks on both sides for 1 to 2 minutes, until browned. Remove from pan and set aside.

Step 4

Clean the mushrooms and coarsely chop them. Place them in a food processor and pulse until finely chopped. Add 1 tablespoon of oil to the same pan in which you seared the steaks, and add the mushrooms. Add the leaves from one sprig of thyme and ½ teaspoon salt. Stir over the heat until the mushrooms begin to release their juices. Cook for about 10 minutes, until all of the moisture has evaporated and the mushrooms have reached a paste consistency (this mushroom paste is called "duxelle"). Set the pan aside.

Step 5

Lay out a piece of plastic wrap. Place two slices of prosciutto in the middle. Spread ¼ of the duxelle over the prosciutto. Put one steak in the middle, then use the cling wrap to bring the corners up to wrap the beef completely. Repeat with the other three steaks. Chill in the fridge for at least 30 min.

Step 6

Remove the puff pastry from the fridge and cut in half. Remove the cling film from the beef, then place in the middle of the puff pastry. Bring the corners of the pastry up to wrap the steak. Turn over so the seam side is down.

Step 7

Crack and separate the eggs. Beat the egg yolks and 1 tablespoon water with a fork. Brush the egg wash over the top and sides of each pastry-wrapped steak. Cover and chill while you make the sauce. Save the remaining egg wash in the fridge.

Step 8

Make the red wine sauce. Heat 2 tablespoons of olive oil in a large pan, then saute the stew meat for a few minutes until browned on all sides.

Step 9

While the beef stew is browning, peel and thinly slice the shallots. Stir in the shallots with the peppercorns, bay leaf, and remaining sprig of thyme. Continue to cook for about 5 minutes, stirring frequently, until the shallots turn golden brown.

Step 10

Add red wine vinegar and let it reduce until it's almost gone. Add the wine and boil for 30 min, until almost completely reduced. Add the beef stock and bring to boil. Reduce heat and simmer while you finish the wellingtons.

Step 11

Preheat the oven to 400 F.

Step 12

While the sauce is simmering, bake the wellingtons. Line a large, rimmed baking sheet with a silicone baking mat or parchment paper. Remove the wellingtons from the fridge and unwrap them, and place them on the lined baking sheet. Score the pastry lightly with a sharp knife and brush with the egg wash again, then bake for 15 to 20 minutes until the pastry is golden brown. Rest for 10 minutes before carving.

Step 13

Finish the sauce by straining the liquid through a mesh sieve, then add salt and pepper to taste.

Step 14

Serve the beef wellingtons with the red wine sauce.