Preheat the oven to 400 and lightly spray or grease a 9" pie pan or quiche dish.

Heat the oil in and saute the apples for about 4 minutes, then add the sausage and cook another 2 minutes or so. Sprinkle with sage and remove from the heat.

In a medium bowl, whisk together the eggs, evaporated milk, and mustard. Stir in the cheese and the apple-sausage mix.

Pour this all into the pie pan and put it in the oven. Bake about 30 minutes. Let it sit about 5 minutes before serving.