I first fell in love with tourte aux pommes de terre (or pâté aux pommes de terre) in a class taught by my friend—and pastry expert—Mitch Stamm. The pie, which is popular in central France, consists of lightly seasoned, thinly sliced potatoes and onion that are coated in heavy cream or crème fraîche and baked inside a double‑crusted pastry shell.
French Potato Pie
There’s no denying that the rich combination makes for a dish that is très décadente. But if you love silky potatoes, buttery pastry, and rich cream, it’s a perfect dish for when you’re in the mood to indulge, and I couldn’t wait to add my own version to the Cook’s Illustrated canon.
I started with the crust. The vast majority of recipes specify puff pastry, and although I found that puff pastry was flaky and delicate on the top of the pie, it was prone to getting soggy underneath the moist filling. Stamm calls for pâte brisée (aka pie dough), as did Julia Child and Simone Beck in Mastering the Art of French Cooking (1961). Sure enough, the thicker, sturdier dough was better at staying crisp on the bottom, especially when I used my colleague Andrea Geary’s foolproof all-butter pie dough.
I built my pie by tossing thin-sliced Yukon Golds with salt, pepper, nutmeg, garlic, and parsley; shingling them over the bottom crust with layers of sliced onion; and enclosing the pie with a vented top crust that I glossed with a beaten egg. After baking, I followed the unusual—albeit common here—step of pouring the cream (I preferred its pure taste to that of tangy crème fraîche) into the vent until the potatoes absorbed as much as I thought they could hold.
As a potato-pie novice, deciding how much cream to drizzle in was a guessing game. It was also tricky to know when the potatoes were tender: Poking a knife into the few slices exposed by the vent didn’t tell me if those deep inside were also done. Finally, the onion didn’t always cook through.
Key Steps to a Tender, Intact Filling
1. SALT onion to draw out excess moisture and soften so it bakes up tender.
2. BOIL potatoes with baking soda for 1 minute to break down their exteriors and release starch.
3. SIMMER potatoes and onion with cream for 5 minutes. Starch from potatoes will thicken cream.
I tackled the potato and onion cookery first. Some recipes call for parboiling the potatoes, others for salting the onions to jump-start the softening process. I found that just a few minutes of boiling was enough to start tenderizing the potatoes so that they were guaranteed to cook through in the oven. And letting the onions comingle with salt drew out their moisture and softened them up perfectly.
Getting the cream into the pie—evenly and in the ideal quantity—was a bigger challenge. The postbake pour was a nifty technique, but it had downsides: Once the potatoes were cooked, they packed together pretty tightly, which prevented the cream from spreading evenly. And because I couldn’t tell how far down the cream had traveled, it was easy to overload the pie, which resulted in a soupy mess upon slicing.
Some recipes call for adding the cream to the potatoes prior to baking the pie, so I decided to try that, with the goal of adding enough to fully coat the potatoes without turning the filling runny.
A Pie to “Defend and Promote”
In France, potato pie is so beloved that a “brotherhood”—La Confrérie du Pâté aux Pommes de Terre Bourbonnais—was created in 2004, with a mission “to defend and promote potato pâté and all the products of the Bourbonnais region and its Saint-Pourçain vineyard.” In addition to holding “Best Potato Pie” competitions, the roughly 100 members—including 26 dignitaries who wear ceremonial dress—keep an admirable roster of activities. Delegations regularly bake pies to donate to community workers such as hospital staff and firefighters; they also appear at events such as food festivals and flea markets. To learn more about the group, visit CooksIllustrated.com/APR21.
I mixed 1 cup of cream with 2 pounds of peeled, sliced, parboiled potatoes; filled the crust; and baked the pie. I could cut this sample into neat wedges, but it begged for more cream. Yet when I incorporated another 1/4 cup, the filling was too loose. So I added baking soda to the potato cooking water. Simmering the potatoes in a mild base would cause their exteriors to degrade and release starch. If I then continued to parcook the potatoes in the cream, the starch would thicken it, helping produce intact slices of pie.
I parboiled the potatoes in the soda-laced water for 1 minute (I didn’t want to overdo it since they would also cook in the cream); drained them; and returned them to the pot along with the salted onion, seasonings, and 1¼ cups of cream. I stirred the mixture over gentle heat until the cream began to thicken, about 5 minutes. It worked like a charm: Once baked, this pie that I adore had just the right creamy richness, and it sliced beautifully.