Preheat the oven to 400°. Press the bottom crust into a 9 inch pie pan and trim the excess with a sharp knife. Set in the fridge until the filling is ready.
In a small bowl mix the sugar, cornstarch, cinnamon, nutmeg and salt. In a medium bowl toss the sliced apples together with the spiced sugar mixture and the lemon juice. Pour into the chilled pie shell.
Generously drizzle about half of the caramel sauce over the apples and then top with the lattice crust. Brush the top crust with the egg wash and sprinkle with course sugar.
Place the pie on a baking sheet to prevent over spilling on the bottom of your oven and bake for 50 minutes, or until the filling is bubbling and the crust is nice and golden brown.
Allow to cool on a rack for 20-30 minutes before drizzling more caramel sauce over the top.
Salted Caramel Sauce
In the microwave, heat the cream until steaming, about 45 seconds. Set aside.
In a heavy bottomed sauce pan heat the sugar, corn syrup and salt over medium high heat until it begins to turn an amber color. Try not to stir it, as that can cause your caramel to crystalize. Instead swirl the pan if you see a spot turning darker faster than the rest of the sugar. Once it is all a nice amber color, turn the heat down to medium and whisk in the butter.
Once the butter has been completely absorbed remove from the heat and slowly add in the warm cream. The mixture will bubble up with the butter and cream, so it's important to make sure it's in a medium pot, not a small one. Whisk in the vanilla and add more salt if needed. Set aside to cool. It may need to be gently warmed in the microwave before pouring on your pie, as it will set up as it cools.