Apple Pie

Variations

• A la mode: Top warm pie with a scoop of vanilla ice cream.
• Dutch apple pie: A butter-flour-sugar crumble instead of a top crust.
• Lattice: Weave the top crust for a pretty finish.
• Caramel apple pie: Add caramel sauce.

Tips

• The two tablespoons of cornstarch are sized for the acid, not for the juice. Thickening says vinegar and tomato cut the starch chains, so an acidic sauce needs more starch — and that the acid is better added after the thickening is set. In a closed pie there is no after: the lemon juice and the apples' own acid are in the bowl with the starch from the start and stay there for the whole bake. That is why a fruit pie carries what looks like a lot of starch for the amount of liquid in it.
• "Until golden and bubbling" is the doneness test for the starch, not the crust. Starch takes up water and swells between 60 and 75°C, and stopping short of that gives partial thickening and a raw, floury taste. Under a lid you cannot see the filling, so the bubbling coming up through the slits is the only signal that the middle reached it. Pulled at the colour you were aiming for, a pie can still have a band of raw starch in the centre.
• The tart apple is structural, and the tip gives only half of it. Soaking is explicit that vinegar, tomato and lemon set pectin firm — an obstruction in beans, and the reason the sauerkraut in bigos survives three hours of stewing. Apple slices are the same case as that cabbage: the acid in a sharp variety plus the tablespoon of lemon juice slows the cell walls collapsing, so you get slices instead of sauce.
• And the fifteen minutes with the sugar does two jobs. Sugar draws water out of the apples by osmosis (what sugar does), and that water is what the cornstarch disperses into while everything is still cold — the guide's "mix starch cold, then boil it", carried out by the fruit instead of in a cup. It also means the filling goes into the shell already wet, so how much juice will appear is no longer a guess.
• Apfelstrudel says to do the exact opposite, and it is right. That page mixes its apples at the last moment because "osmosis pulls the water out and the filling floods", and lays fried crumbs underneath to absorb what still comes: one thin sheet has nowhere to put juice. The difference between the two is a starch. This pie captures the same juice rather than avoiding it.
• Tarte Tatin is another answer again, and it names this pie as its inverse — there the apples give up their water in the pan before the oven and the pastry is a lid that never meets liquid. Blind baking the shell first, as quiche and pastel de nata do, is another. One problem — a wet filling over a pastry base — and each dish answers it somewhere else in the method.
• The slits, and then the thirty minutes. Steam that cannot leave condenses under the top crust and pins it at 100°C, which is the temperature at which nothing browns (browning). And a starch gel only firms as it cools: cut hot, the filling runs not because it is under-thickened but because it has not set yet. Cheesecake waits four hours for the same reason, on a filling set by egg instead.
• Use tart apples (Granny Smith) so it isn't cloying.
• Cornstarch thickens the juices so the filling doesn't run.
• Cut slits in the top so steam escapes and the crust stays crisp.
• Always cool it well before slicing so the filling holds.
• If the crust edges brown too fast, shield them with foil.