Procedures

1. 1

   Preheat the oven to 350°F.

2. 2

   In a large bowl, combine the beef, truffle butter, and salt. Mix with a fork or your fingers until the butter is just incorporated. Form the beef into 4 patties. Lay a slice of pancetta over each patty.

3. 3

   Preheat a large, ovenproof skillet (preferably cast iron) over medium-high heat until hot. Put the burgers in the skillet, pancetta-side down, and cook for about 4 minutes per side for rare, 5 minutes per side for medium-rare.

4. 4

   Put the cheese on top of the burgers and place the skillet in the oven until the cheese is melted, about 5 minutes.

5. 5

   Place the burgers on the bottom bun halves, top with the tomato slices and radicchio, and cover with the top bun halves.