A just-baked apple pie with a mountainous golden crust is nice if there's a mountain of perfectly cooked apples under the hood, but often there is, instead, a yawning gap between crust and filling that makes each serving seem skimpy and sad. The cause is often the steam slowly given off by thick apple slices as they bake; steam pushes the crust up as the fruit cooks down.The solution: The examples above show that thinly sliced apples, rather than wedged or cubed fruit, deliver a trimmer pie profile. Because sliced apples cook quickly, steam is allowed to escape without lifting the crust. Arrange slices tightly in the pie shell, layering by hand as you would when making a tart, to minimize air pockets than can also produce an uneven pie. With nicely packed fruit you don't need to overfill; a good ratio is about 3 pounds of apples per pie. Remember to vent the crust: Three large slits across the top will expel steam during baking, leaving the filling even and juicy throughout.