Heat a saute pan, over medium heat. Season both sides of the foie gras with salt and pepper. Season the flour with salt and pepper. Dredge the foie gras in the flour, coating completely. Sear the foie gras for 1 minute on each side. Remove from the pan and drain on paper towels. Add the apples and sugar to the foie fat. Saute for 1 minute. Remove the pan from the heat and add the Calvados. Place back on the heat and flame the liquor. Shake the pan back and fourth several times until the flame dies out. To assemble, place the croutons in the center of each plate. Place a piece of foie gras on top of a crouton. Spoon the apple sauce over the foie gras and serve.