In a small bowl place the heavy cream and whisk it for 3 to 5 minutes, or until it is softly whipped. Add the egg yolks and the Calvados, and whisk them in. In each oyster half shell place the diced apple. Place the oyster meat on top. Cover it with the cream mixture. Place the oysters on a flat sheet and broil them for 1 to 2 minutes, or until the cream mixture is golden.