Christmas Beef Wellington

Pat the beef dry with paper towels.

Season the beef all over with salt and black pepper.

Heat 1 tablespoon oil in a large skillet over high heat.

Sear the beef on all sides until browned, about 2 minutes per side.

Transfer the beef to a plate and let it cool.

Brush the cooled beef with Dijon mustard.

Melt the butter with the remaining oil in the skillet over medium heat.

Add the shallots and garlic.

Cook until softened, about 3 minutes.

Add the mushrooms and thyme.

Cook, stirring often, until the mushrooms release their liquid and the pan is dry, about 12 to 15 minutes.

Season the mushroom mixture with salt and black pepper.

Spread the mushroom mixture on a plate and let it cool completely.

Lay a large sheet of plastic wrap on the counter.

Arrange the prosciutto slices on the plastic wrap in an overlapping rectangle.

Spread the cooled mushroom mixture evenly over the prosciutto.

Place the beef along one edge of the prosciutto rectangle.

Roll the prosciutto and mushrooms tightly around the beef using the plastic wrap.

Twist the ends of the plastic wrap to secure the roll.

Refrigerate the wrapped beef for 20 minutes.

Lightly flour the counter.

Roll the puff pastry into a rectangle large enough to enclose the beef.

Remove the plastic wrap from the chilled beef roll.

Place the beef in the center of the pastry.

Brush the pastry edges with beaten egg.

Fold the pastry around the beef and seal the edges.

Place the Wellington seam-side down on a parchment-lined baking sheet.

Brush the pastry with beaten egg.

Chill the Wellington for 10 minutes.

Preheat the oven to 200°C.

Bake the Wellington until the pastry is deeply golden and the center reaches 50 to 52°C for medium-rare, about 35 to 40 minutes.

Rest the Wellington for 15 minutes before slicing.

Arrange the sliced Wellington on a serving platter.

Garnish the platter with fresh cranberries and rosemary sprigs.