Remove the tough outer leaves of the artichoke and remove the choke with a spoon. Slice the artichoke hearts into thin slices (about 1/8-inch thick).
Clean the porcini mushrooms and remove the stems. Cut into "batonnets" slices that are 1 1/2 inch long by 1/4-inch thick.
In a saute pan saute the artichokes in 2 tablespoons olive oil, seasoning with salt and pepper. Cook until the artichokes are slightly caramelized. In another pan, saute the mushrooms in 3 tablespoons olive oil, seasoned with salt and pepper until they are slightly caramelized.
Lightly flour the foie gras on both sides. Sear in a medium hot, dry saute pan about one minute on each side.
To plate the dish, place one cup of greens on each plate. Evenly divide the artichokes and mushrooms and place on top of the greens. Top each with a slice of foie, sprinkling a line of coarse salt over the top of each foie piece. Spoon about 2 tablespoons of the Vinaigrette over each salad. Sprinkle with walnuts.
Combine the lemon juice, soy sauce and truffle juice. Whisk in the olive oil. Season with salt and pepper.