Heat olive oil in a frying pan over medium heat. Add garlic and sauté for 1 minute.

Add chopped mushrooms and thyme, cook until moisture evaporates, about 10 minutes.

Season with salt and pepper, then let cool.

Season the beef with salt and pepper. Heat a frying pan until hot, then sear the beef on all sides for 2-3 minutes each side.

Remove from heat and let cool.

Lay prosciutto slices on a sheet of cling film, slightly overlapping.

Spread the cooled duxelles over the prosciutto.

Place the beef on top and roll tightly using the cling film. Chill for 15 minutes.

Roll out the puff pastry on a floured surface to about 3mm thick.

Unwrap the beef from cling film and place in the center of the pastry.

Wrap the pastry around the beef, sealing the edges with beaten egg.

Preheat the oven to 200°C (400°F).

Place the wrapped Wellington on a baking sheet, brush with egg wash, and score the top.

Bake for 25-30 minutes until golden brown and the internal temperature reaches 55°C (130°F) for medium rare.

Let the Wellington rest for 10 minutes before slicing.

Serve with your choice of sides.