In a large bowl, combine gingerbread mix, water, egg, and diced apples. Spoon into a 9-inch square pan which has been sprayed with cooking spray.
In a small bowl, combine butter, brown sugar, flour, cinnamon and salt with a fork until crumbly. Sprinkle this evenly over gingerbread batter.
Bake in a preheated 350-degree oven for 35 to 40 minutes or until toothpick inserted near center comes out clean. Serve warm or cold with a spoonful of whipped cream. May also garnish with a fresh orange slice.