Step 1In a bowl, knead together the chicken, truffle pâté and oil, bread crumbs and salt. Divide the mixture and form it into four patties. Set aside.
Step 1In a dry skillet, toast the caraway seeds over medium heat, shaking or stirring frequently, until lightly browned and aromatic, about 3 minutes. Remove from heat. Grind the seeds to a powder using a spice grinder or mortar and pestle.
Step 2In a bowl, whisk together the caraway powder, creme fraiche, buttermilk, lemon juice, mustard and a pinch of salt, or to taste. This makes a scant ¾ cups dressing, which will keep, covered and refrigerated, up to 5 days.
Step 1Heat a grill or grill pan over medium-high heat until hot. Meanwhile, season each chicken patty lightly with salt and pepper on each side.
Step 2Lightly char the cooked bacon on the grill until warmed through. Remove and set aside.
Step 3Cook the patties until charred and cooked through, about 5 minutes on each side depending on the thickness of the burgers. Place a spoonful of sauerkraut on top of each patty, followed by 3 slices of cheese and 3 strips of bacon. Set aside so the heat from the burgers can begin to melt the cheese. Toast each half of each bun.
Step 4To assemble the burgers, spread 1 tablespoon of the dressing on each half of each bun, or more if desired. Place about ½ cup watercress on the base of each bun. Top the watercress with a prepared burger, then season with a twist of freshly ground pepper. Top with the remaining bun half. Serve immediately.