- 1 1/2 pounds ground sirloin
- 1 shallot, finely chopped
- 2 tablespoons finely chopped fresh flat-leaf parsley
- 1 tablespoon Worcestershire sauce (eyeball it)
- Salt and freshly ground black pepper
- Extra-virgin olive oil (EVOO), for drizzling
- 3 tablespoons butter
- 1/2 pound cremini or white mushrooms, sliced
- 1/2 cup dry sherry
- 2 tablespoons Dijon mustard
- 4 eggy rolls, split and toasted
- 1 bunch watercress, chopped
- 1/2 cup chopped cornichons or baby gherkin pickles
- 1/2 pound truffle mousse pate
- In a medium bowl, mix together the meat, shallot, parsley and Worcestershire sauce; season with salt and pepper. Score the meat into 4 equal portions and then form into large patties. Heat a drizzle of EVOO in a large nonstick skillet over medium-high heat. When the pan is screaming hot, add the patties and cook for 4 minutes on each side for medium rare, 6 minutes on each side for medium well.
- Meanwhile, place a medium skillet over medium heat. Melt 2 tablespoons butter in a drizzle of EVOO, add the mushrooms and cook until tender, about 6 minutes. Pour in the sherry and let it cook off, about 30 seconds. Season the mushrooms with salt and pepper and remove from the heat.
- Stir together the mustard and remaining 1 tablespoon butter. Spread the Dijon butter liberally on the bun bottoms. Top with the watercress, a burger patty, a pile of mushrooms and a few chopped cornichons. Spread the mousse pate on the bun tops and set them into place.