Prepare several sheets of parchment, one per per-son. In the center of each, place several fingerling potatoes, a few slivers of truffle butter (or fresh butter and fresh-grated truffles), salt, pepper, and a few sprigs of fresh thyme. Fold the parchment together over the ensemble and tuck the ends underneath. Place on a baking sheet in the oven at 400°F for a half hour or so, until steaming and tender. Serve papillotes alongside a freshly-seared steak, or all alone with a salad.