Mix ground beef, bread crumbs, shallot, Dijon mustard, egg, garlic, salt, and black pepper together in a large bowl. Refrigerate mixture to incorporate flavors, 20 minutes to 2 hours.
Form ground beef mixture into 6 patties.
Heat a skillet over medium heat; lay pancetta slices in a single layer in the hot skillet. Cook until pancetta begins to sweat, 3 to 5 minutes.
Remove pancetta from skillet and keep warm.
Preheat grill for medium heat and lightly oil the grate.
Cook patties on the preheated grill until burgers are cooked to your desired degree of doneness, about 4 minutes per side for medium-well burgers. An instant-read thermometer inserted into the center should read 160 degrees F (70 degrees C).
Place 1 burger into each of the buns; top burger with a pancetta slice.
