Step 1: Prepare the Beef
Season the beef generously with salt and pepper.
Heat olive oil in a skillet over medium-high heat.
Sear the beef on all sides, 2–3 minutes per side, until browned.
Remove from heat, let cool, then brush with Dijon mustard.
Step 2: Make the Mushroom Duxelles
Finely chop mushrooms (and shallots/garlic if using).
Sauté in butter over medium heat with salt and pepper.
Cook until moisture evaporates and mushrooms form a paste-like consistency.
Allow duxelles to cool completely.
Step 3: Assemble the Wellington
If using pâté, spread it evenly on plastic wrap.
Layer mushroom duxelles on top of the pâté.
Place the beef on the duxelles and roll tightly using plastic wrap into a uniform log.
Roll out puff pastry and place beef log in the center.
Fold pastry over the beef, trim excess, and seal edges.
Brush pastry with beaten egg for a golden finish.
Chill assembled Wellington for 15–20 minutes to prevent pastry leakage.
Step 4: Bake the Wellington
Preheat oven to 400°F (200°C).
Place Wellington on parchment-lined baking sheet.
Bake 25–35 minutes, depending on desired doneness (medium-rare: 125–130°F / 52–54°C).
Let rest for 10 minutes before slicing.