Pat the beef steaks dry with paper towels. Season both sides with salt and pepper. Heat olive oil in a skillet over medium-high heat. Sear the beef for about one minute on each side. The outside should brown but the inside stays rare. Remove the beef and let it cool slightly.

Make the Mushroom Mixture

Melt butter in the same skillet. Add chopped mushrooms and cook until moisture evaporates. Stir in garlic and thyme. Cook for another minute until fragrant. The mixture should look thick and dry. Let it cool before using.

Brush Beef with Mustard

Use a pastry brush to spread Dijon mustard over each steak. This step adds flavor and helps the filling stick. The mustard also gives the beef a slightly tangy taste that pairs beautifully with mushrooms.

Wrap with Prosciutto

Lay slices of prosciutto on a piece of plastic wrap. Spread a spoonful of the mushroom mixture over the prosciutto. Place the beef steak on top. Wrap everything tightly using the plastic wrap. This layer keeps the beef moist during baking.

Prepare the Puff Pastry

Roll out the puff pastry sheet on a lightly floured surface. Cut it into four equal squares. Each square should be large enough to wrap around the beef completely.

Wrap the Mini Wellingtons

Place one wrapped steak in the center of each pastry square. Remove the plastic wrap first. Fold the pastry around the beef and seal the edges tightly. Make sure the seam stays underneath.

Add Egg Wash

Place the wrapped Wellingtons on a baking sheet lined with parchment paper. Brush the tops with beaten egg. This step helps create the golden, shiny crust.

Bake Until Golden

Preheat the oven to 400°F (200°C). Bake the Mini Beef Wellingtons for about 20–25 minutes. The pastry should become golden and crisp. The beef inside will stay tender and juicy.

Rest Before Serving

Remove the Wellingtons from the oven and let them rest for five minutes. This allows the juices to settle inside the beef. Then slice carefully and serve warm.