It’s always a good day when I get a handwritten personal letter. It’s even better when that letter comes from a reader sharing food memories or treasured family recipes.

I received such a letter recently from Vivian Russom in Tecumseh. Along with a recipe for potato casserole, Ms. Russom shared a memory of a pie her mother used to bake — a vinegar pie.

“It sounds weird, but it was actually good,” wrote Ms. Russom. “I don’t have the recipe and haven’t seen one since I was a child. Have you ever heard of a vinegar pie?”

Vinegar pies were new to me, but a little bit of research shows that they’ve been around since the mid-19th century. A vinegar pie is a very simple dessert; a custard pie flavored with apple cider vinegar.

When baking a vinegar pie, you are transported back in time. Now you’re a pioneer - maybe Ma Ingalls. It’s the deepest, coldest part of the winter. You don’t have access to fresh fruit. You’ve exhausted your supply of fall apples.

Vinegar pie, like bean pie or the mock apple pie from the Ritz cracker box, is a recipe born of necessity. It was dreamed up out of a lack of resources, and it tastes far better than it sounds.

When you take the first bite of a slice of vinegar pie, your first thought is: “Oh, there’s the vinegar.” But with each subsequent bite (and I’ve eaten quite a few slices now, in the name of errr… research) you start to taste the apple flavors and notice the silky custard texture. You marvel at just how delicious this pie of our ancestors actually is.

If you want to be true to the spirit of vinegar pie, eat it as is. I cheated just a little bit, and acknowledging just how lucky we are to have access to fresh fruit all year round, I accented the pie with some raspberries. It would taste delicious with sliced strawberries or tart blackberries too.

A note on the filling: make sure to keep the custard at a moderate temperature when cooking it on the stovetop, and don’t let it come to a boil once you’ve added the egg mixture. Otherwise the eggs will curdle, ruining the custard.

Vinegar pie (slightly adapted from Gourmet Magazine)

• 1/2 recipe pastry dough (or refrigerated pie crust)
• 2 large eggs
• 1 cup sugar
• 1 tablespoon all-purpose flour
• 1 cup cold water
• 2 tablespoons cider vinegar
• Cinnamon for dusting

Accompaniment: lightly sweetened whipped cream or fresh berries

Make pie shell:

Roll out pastry dough on a lightly floured surface with a floured rolling pin into a 12-inch round. Fit dough into pie plate and trim excess, leaving a 1/2-inch overhang. Fold overhang inward and crimp against the plate rim. Prick bottom of shell all over with a fork and chill 15 minutes.

Preheat oven to 400 degrees.

Line shell with foil and fill with pie weights. Bake in middle of oven until edge is pale golden and sides are set, about 20 minutes.

Make filling while shell bakes:

Whisk together eggs and 1/4 cup sugar in a bowl until blended well. Whisk together flour and remaining 3/4 cup sugar in a 1-quart heavy saucepan, then whisk in water and vinegar. Bring to a boil, whisking until sugar is dissolved. Add to egg mixture in a slow stream, whisking constantly.

Pour filling into saucepan and cook over moderate heat, stirring constantly with a wooden spoon, until filling coats back of spoon and registers 175 degrees on an instant-read thermometer, 12 to 15 minutes. (Do not boil.) Immediately pour filling into a 2-cup glass measure. If pie shell is not ready, cover surface of filling with a round of wax paper.

Reduce oven temperature to 350 degrees, then pour hot filling into baked pie shell in middle of oven and cover rim of crust with a pie shield or foil (to prevent over-browning). Bake pie until filling is set, 15 to 20 minutes, then cool completely in pan on a rack. Dust evenly with cinnamon.

Jessica Webster leads the Food & Grocery section for AnnArbor.com. Reach her at JessicaWebster@annarbor.com. You also can follow her on Twitter or subscribe to AnnArbor.com's email newsletters.