From Filling a Can to Filling a Pie

• For anyone who's ever tried to shake pumpkin puree from a can, the idea of thickening it might seem absurd. Canned pumpkin is made from varieties that are denser and richer-tasting than the familiar Halloween pumpkins, but much of its moisture is cooked out during processing. The result is a fine, thick paste with a deep color, much darker than uncooked pumpkin thanks to the darkening effect of cooking. Although pumpkin is naturally sweet, turning it into a pie filling requires a number of additional ingredients.

The Basic Mixture

• Cooked pumpkin puree is high in naturally occurring sugars, but it certainly isn't dessert-sweet. Bringing it to that point requires sugar or other sweeteners. Brown sugar is a common choice because it has a distinct flavor, as well as sweetness. Some cooks also add corn syrup, honey or maple syrup. Further flavors come from warm spices such as cinnamon, cloves, ginger and nutmeg or mace, either added separately or as a preblended spice mix. Cream or evaporated milk adds richness and mellows the earthiness of the pumpkin, and finally eggs help bind and thicken the entire mixture.

Egg-Thickened Custards

• Pumpkin pie is distinctly different from a silky-smooth creme brulee or a savory quiche, but they're all custards. Any liquid that's thickened at least partially by eggs is considered a custard. When eggs are beaten into pumpkin puree to make pumpkin pie filling, their proteins are finely dispersed throughout the mixture. As the filling cooks in the oven's heat, those eggs set just as they would in your breakfast skillet. Since they're diluted, they can't arrive at a firm egg texture and instead set into a loose gel. This fine web of proteins immobilizes the liquid in the pie filling, creating a soft but firm and sliceable pie.

A Few Tips

• Some bakers simply pour cold filling into an unbaked pie shell and slide it carefully into the oven, but this often results in a mushy crust. It's more prudent to bake the crust separately until it begins to crisp and then fill it and finish the pie. If the edges become too brown, cover them loosely with foil. Cooking the pie filling over a double boiler until it begins to thicken is another good strategy. Pour the filling into your partially baked pie shell, and finish them both quickly in the oven. No matter which method you prefer, your pie is finished when the edges of the filling are set and the middle is still slightly jiggly.