Bring steaks to room temperature. Coat steaks lightly with olive oil and season both sides with salt and pepper (press in with your hands).
In a heavy frying pan (I use my cast-iron frying pan) over medium-high heat, heat 2 tablespoons olive oil. Sear the steaks, moving them with tongs a little so they do not stick to the bottom, for 2 minutes per side or until brown and crisp on the outside. Steak will be partially cooked - do not overcook. Remove from heat and refrigerate steak, covered, until well chilled, about 1 hour.
In a large frying pan over medium heat, melt butter. Add shallot or green onions and garlic; saute approximately 3 minutes or until slightly softened. Add mushrooms, thyme, parsley, and salt and pepper to taste. Cook, stirring, until mushrooms are lightly browned and their liquid is evaporated. Remove from heat and transfer mushroom mixture to a bowl to cool completely; set aside.
On a lightly floured surface, roll out each puff pastry into two (14-inch) squares. Trim edges to form two (13-inch) squares and cut each square into four (6 1/2-inch) squares.
Working with one square of puff pastry at a time (keeping other covered), spread 1/8th of mushroom mixture on the pastry, leaving a 1/2-inch edge on all sides. Place chilled steak in the center of the mushroom mixture; pressing it down gently. Wrap two opposite corners of puff pastry over the steak, overlapping them. Seal seam with egg wash. Wrap remaining two corners of pastry over steak and seal with egg wash. Wrap the pastry up over the steak and seal the edges. Place seam-side down on a non-stick baking sheet. Brush the tops with the egg wash. Repeat with remaining 7 steaks. Cover loosely and refrigerate at least 1 hour or up to 1 day.
NOTE: Decorations for the Beef Wellingtons using the scraps from the puff pastry. Cut pastry into shapes with a cookie cutter or cut into leaf shapes with a knife and "glue" to the top of each Beef Wellington with some of the egg wash. Brush top of decoration with additional egg wash.
When ready to bake, brush top and sides of each Beef Wellington with some remaining egg wash. Preheat oven to 425 degrees F. Bake approximately 15 to 20 minutes or until pastry is golden and the internal temperature registers 120 to 130 degrees F. on your instant-read meat thermometer:
Rare - 120 degrees F
Medium - 130 degrees F
What constitutes rare and medium-rare cooked meat? To satisfy government home economists, the Beef Council says rare beef means an internal temperature of 140 degrees F. Well, that is ok if you like well-done and dry meat. If you like moist, rosy meat (like I do), rare begins when the internal temperature registers 120 degrees F. and starts to become medium rare at 125 or 130 degrees F. To cook your meat properly, you must purchase and use a good instant-read digital meat thermometer.
While Beef Wellington are baking, prepare Peppercorn Sauce.
To serve, spoon some of the Peppercorn Sauce on each individual plate. Place one Beef Wellington in the center. Drizzle a little more sauce over the top and garnish with a dill sprig.
Makes 8 servings.
In a medium frying pan over medium heat, melt butter. Add shallot or green onions, green peppercorns and saute until onions are soft. Add brandy and cook until liquid is reduced by half. Add cream and simmer for 2 minutes. Season with salt, pepper, and dill.
Beef Wellington with Peppercorn Sauce Recipe: https://whatscookingamerica.net/beef/beefwellington.htm