In a stainless steel bowl, combine pineapple juice, syrup & lemon juice. Freeze in an ice cream/sorbet machine according to the manufacturer’s instructions.
Heat oil in a small nonstick fry pan over medium high heat. Add pineapple & distribute evenly in pan. When pineapple starts to carmelize, sprinkle with sugar & toss. Continue sautéing until pineapple is evenly caramelized. Allow to cool to room temperature.
Slice the foie gras into 8 slices, each about 1 inch thick. Place the slices on a large plastic wrapped plate. Score slices in a criss cross pattern on one side. Season with a little sea salt and freshly ground white pepper on each side
To sear, use two 8 inch nonstick fry pans and place on the stove over high heat. When the pan starts to lightly smoke, remove from heat. Carefully place 4 pieces of foie gras in each pan, scored side down, & sear for 1 ½ minutes. Pour off excess fat. Turn over & cook for another minute. Remove from heat & put foie gras onto a clean towel to absorb excess fat. Season with a pinch of coarse salt.
In a small pot over medium heat, reduce vinegar to ½ cup. Stir occasionally to ensure the vinegar does not burn on the bottom. Remove from heat & allow to cool. Place in an airtight container & refrigerate until needed.
In the centre of a large plate, spoon a little of the caramelized pineapple. Place a piece of seared foie gras on top & sprinkle with a little coarse black pepper. Scoop a quenelle of pineapple sorbet and out on top or to the side. Drizzle a little balsamic reduction around & serve immediately