Combine the ground beef with salt and pepper. Divide the mixture into four equal portions and shape them into patties about ¾ inch (2 cm) thick.
Heat a skillet over medium-high heat. Cook the patties for about 2-3 minutes per side, until lightly browned but still juicy inside.
Spread Dijon mustard on top of each patty and let them cool slightly.
Lay out a sheet of plastic wrap. Place a slice of prosciutto on it, then spread with mushroom duxelles. Place a mustard-coated patty in the center and wrap it with the prosciutto.
Roll out the puff pastry and cut it into four equal squares. Wrap each patty in a square of puff pastry, sealing the edges well to prevent them from opening during baking.
Brush the pastry with a beaten egg and place on a baking sheet lined with parchment paper. Bake at 400°F (200°C) for about 15-18 minutes, or until golden brown.
Meanwhile, halve the hamburger buns and toast them in a dry skillet or with a little butter until golden brown on the cut sides.
Prepare the vegetables: slice the tomato and red onion into thin rings.
Assemble the burgers: place a lettuce leaf on the bottom bun, then top with a Wellington-style patty. Add tomato and red onion slices, and finish with the top bun.
Serve immediately, preferably with a flavorful sauce or french fries. Tip: For an extra special flavor, serve with a little extra Dijon mustard or a red wine reduction.
To provide the best experiences, we and our partners use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us and our partners to process personal data such as browsing behavior or unique IDs on this site and show (non-) personalized ads. Not consenting or withdrawing consent, may adversely affect certain features and functions.
Click below to consent to the above or make granular choices. Your choices will be applied to this site only. You can change your settings at any time, including withdrawing your consent, by using the toggles on the Cookie Policy, or by clicking on the manage consent button at the bottom of the screen.