Mix egg yolk with breadcrumbs. Cut the eggplant into 8 thin slices, dip them in the breadcrumb mixture and fry them. Cut slice the apple into 8 pieces. Divide the cheese into 4 pieces. Place 1 slice of eggplant, 1 apple slice, a piece of cheese, another slice of eggplant and another apple slice on each of four skewers. Bake in 350°F oven until the cheese begins to melt and serve immediately.