The answer was pretty obvious when I stumbled over it: pie.
There are lots of recipes for traditional sweet potato pie. As usual I'm looking for recipes that don't require I buy anything special. Pie crust ("short crust" to my friend Emily) is easy, I've always got that stuff and other basic baking needs. I found a lot of recipes that use sour cream or evaporated milk, which I don't keep around. The one I settled on uses buttermilk.
I keep buttermilk powder around when I can afford it, but you can make a buttermilk substitute by adding one tablespoon of vinegar to a scant cup of milk ("scant" means "not quite the whole measure" - just take a tablespoon of milk out before you add the vinegar.) This gives the properties of buttermilk for baking, and the taste is close. It will clump and look soured when you add the vinegar, which is what you want.
The recipes I found also use pie crust or graham cracker crust interchangeably. Graham cracker crust is really simple to make if you don't want to muck with rolling out dough. It's just crushed graham crackers and butter.
Most of the recipes I found used fresh baked and mashed sweet potatoes, and what I have are canned in syrup. They mash very well, and the syrup just means a sweeter pie. The recipe I started with is from bakingbites.com, and here's what I ended up with. If you're using buttermilk powder, follow the directions on the can for adding liquid and the powder:
Graham Cracker Crust
6 Tbsp butter or margarine
About 24 graham crackers, crushed to make 1 1/2 cups of crumbs
1/4 cup sugar
Cinnamon, allspice, or nutmeg (optional)
Crush the graham crackers by putting them in sealable bag and rolling them until they're crumbs. A food processor or blender also works well.
In a small saucepan or the microwave, melt 6 tablespoons of butter. Measure 1 1/2 cups of graham cracker crumbs into a medium bowl. Add 1/4 cup of sugar to the graham crackers. Add the melted butter. Add a little cinnamon, nutmeg, or allspice to the crumbs for a spiced flavor. Stir or blend together with your hands. Press into the pie plate or other pan. To pre-bake the pie crust, bake for 8 to 10 minutes in a preheated 350 degree F. oven.
Buttermilk Sweet Potato Pie
1 15 ounce can of sweet potatoes, drained
1 cup buttermilk
1/4 tsp nutmeg
1/4 tsp salt
2 tsp vanilla extract
3/4 cup brown sugar
3 large eggs
2 Tbsp flour
1 9 or 10 inch pre-baked pie crust
Preheat oven to 350 F.
In a blender or food processor, blend the sweet potatoes and buttermilk to a smooth puree. Add all ingredients except flour and blend smooth. Add flour and pulse the blender until it's just incorporated (don't over blend, it will make the pie tough).
Place the pie crust on a baking sheet and place baking sheet on the middle rack of a preheated oven. Pour filling into pie crust (it is thin enough that it will slosh if you put it in the pie crust and attempt to carry it over to the oven).
Bake for 50-55 minutes, until pie is set and jiggles only very slightly when the pan is bumped. You may want to put a crust guard (foil works) on the exposed pie crust to keep it from burning.
Cool on a wire rack to room temperature. Refrigerate for at least 2 hours, or overnight, before serving.
This is close enough to pumpkin pie that the kids don't notice the difference! A little whipped cream dresses it up.
For the pie pictured here I used a Wal-Mart "Great Value" pre-fab pie crust. I won't be buying that particular crust again. The first shrank up so bad on baking that what I had was a thick tart crust with barely any sides. So I rolled out the second crust a bit and left it laid over the edges of the pie pan for shrinkage, and it didn't shrink. It did, however, bubble up badly on baking (despite pricking it), which has left some shallow spots in the pie.
The good news is the kids don't care too much, they just like pie. And there's nothing wrong here that sufficient application of whipped cream won't fix.
I made this pie today and remembered to take a picture of a pretty one. I've also tweaked the recipe a little.
The pie won't stay puffy, by the way. Custard pies will "fall" as they cool.