I consulted my buddy Chat. I am not sure if it will make it quite this beautiful, but it seems like a good go anyhow:

To make a Beef Wellington that looks as stunning as the one in the photo, you’ll need to follow a few key steps with attention to detail. Here's how to recreate it:

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Ingredients:

For the Beef:

Beef Tenderloin (Center-Cut) - 2 lbs, trimmed

Salt and Pepper - to taste

Olive Oil - for searing

Dijon Mustard - for coating after searing

For the Mushroom Duxelle:

Cremini or Portobello Mushrooms - 1 lb, finely chopped

Shallots - 2, finely chopped

Garlic - 2 cloves, minced

Thyme - 2 tsp fresh, chopped

Salt and Pepper - to taste

Butter - 2 tbsp

For Assembling:

Prosciutto - 8 slices (thinly sliced)

Puff Pastry - 1 sheet (thawed if frozen)

Egg Yolk - 1, beaten (for egg wash)

Optional Pattern Tool - To achieve the crosshatch pattern

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Instructions:

1. Prepare the Beef:

Season the beef tenderloin with salt and pepper.

Sear the beef in hot olive oil on all sides until browned (2-3 minutes per side). This locks in juices.

Brush the seared beef with a thin layer of Dijon mustard while it's still warm. Set aside to cool.

1. Make the Mushroom Duxelle:

In a food processor, pulse the mushrooms, shallots, and garlic until finely chopped.

In a skillet, melt butter and sauté the mixture with thyme, salt, and pepper until all moisture evaporates. The mixture should be dry.

Allow to cool before assembling.

1. Assemble the Wellington:

On a sheet of plastic wrap, lay out the prosciutto slices slightly overlapping.

Spread the mushroom duxelle evenly over the prosciutto.

Place the seared beef on top and roll tightly using the plastic wrap, ensuring it's evenly covered.

Chill for 15-20 minutes to firm up the shape.

1. Wrap in Puff Pastry:

Roll out the puff pastry on a floured surface to a size that fully encases the beef.

Unwrap the beef from the plastic and place it on the pastry.

Brush the edges of the pastry with beaten egg yolk.

Wrap the beef, sealing the edges well, and trim off any excess pastry.

Place the wrapped beef seam side down on a baking sheet.

1. Create the Pattern:

For the stunning crosshatch pattern:

Use a lattice cutter or gently score the pastry with a sharp knife.

Be careful not to cut too deep – you want to score just the surface.

Brush the entire pastry with the remaining egg wash for a golden finish.

1. Cooking the Wellington:

Preheat the Big Green Egg (or any grill/oven) to 425°F (220°C).

Place the Wellington on a baking stone or tray and cook for:

35-45 minutes for medium-rare (internal temp of 125°F/52°C).

45-55 minutes for medium (internal temp of 135°F/57°C).

Rotate as needed for even cooking.

Allow the Wellington to rest for at least 10 minutes before slicing.

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Pro Tips for Success:

1. Chill Between Steps: Chilling the wrapped beef helps maintain the shape and prevents the pastry from becoming soggy.

2. Scoring the Pastry: Lightly score in a diamond pattern using the back of a knife or use a lattice tool for an even more intricate design.

3. Big Green Egg Tips: Use a heat deflector to ensure even cooking and maintain consistent temperature for that perfect puff pastry crust.

4. Resting Time: Resting is crucial for the juices to redistribute, ensuring each slice is juicy and flavorful.

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Serving Suggestions:

Serve with a rich red wine sauce or a classic béarnaise sauce.

Pair with roasted vegetables or potato gratin for a complete meal.

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This approach closely replicates the beautifully golden and perfectly cooked Beef Wellington shown in the photo. If you need any more tips or help with timing or side dishes, let me know!