Plum Wähe: A Swiss Plum Custard Tart

My grandmother makes food that is proof of the goodness of simplicity. She doesn’t fuss around with trendy ingredients or laborious techniques. Instead, she does everything with the careful precision that comes from her years of experience, and pays attention to even the minutest details, both of which result in dishes that are nothing short of masterpieces.
As a child, I loved nothing more than to be in her tiny kitchen, watching as she whipped up treat after treat. There was a crispy potato rosti with meltingly sharp Gruyere, which we sometimes ate for lunch. There were crackly brownies covered in thick, ridged frosting, which I’d sneak from the ever-present tin on the counter.
For special occasions, she’d make a Hungarian Zserbo torte, with layers of spiced walnut and jam between thin sponge cake, topped with a dark ganache. She could (and still does) produce fluffy, expertly shaped challahs with the most golden of crusts out of seemingly thin air, and her light-as-anything chocolate mousse is still, to this day, one of my favorite desserts.
But of all the things my grandmother makes, this plum tart is my favorite. It isn’t a year-round occurrence; the tiny, dusty purple Italian plums used to make this are only in season from August to September. But when she does make this, well, everything falls into place.
The plums, once tart and firm, with beguiling green interiors, are transformed by the heat. They cook down, slump in their skins and release puddles of heady magenta juice. They turn inexplicably sweet, but retain a touch of their sourness and they mingle with the lightly sweet custard and sit like proud purple jewels against the edges of the tart, which brown and puff like the exterior of a clafoutis.
It is like a combination of all the best dessert characteristics you could hope for: the crispy bottom of an unweighted tart, the bronzed edges of a flaugnarde and the juicy, syrupy fruit reminiscent of a slaved over pie. But it is all so simple- it takes mere minutes to make!- that it is sure to become a summer classic, a dessert to serve and to savor as it proves, once again, that sometimes, simplest is best.

Yields: one rectangular tart the size of a half sheet pan, serving 12-14 (or 2 round 8” tarts) 

Why I love this recipe: my grandmother’s dough uses oil and vinegar to make a flaky crust and baking it on a high heat crisps it up beautifully. The plums, which turn sweet, juicy and are flavored with just a touch of nutmeg, are covered in an eggy cream mixture that bakes into a fluffy, creamy custard. Be sure to sprinkle the tart with sugar right before serving it. 

Notes: this dough may be different than what you’re used to, but don’t be afraid of it; the flavor of the vinegar all but disappears and it helps contribute to a flaky, crispy dough. The dough will be hard to wrest into the pan, but it needs to be very thin in order to crisp up, so just go with it. This is a traditional Swiss tart, known as Zwetschgenwähe. It’s sold by the slice or square in bakeries all over the country. It’s made with Italian prune plums- “zwetschgen”- although sometimes apricots are used. It will keep overnight, covered for a day, at room temperature, or in the fridge for 2-3 days.  

For the dough: 

• 1 cup vegetable oil
• 1 cup water
• 2 tablespoons vinegar
• 1 teaspoon fine sea salt
• 1 tablespoon sugar
• approx. 2 1/2-3 cups all purpose flour

For the filling:

• 1 cup heavy cream
• 25-28 Damson/Italian prune plums
• 3 eggs
• 1 tablespoon vanilla extract
• 1/2 teaspoon fine sea salt
• 1/3 cup granulated sugar
• 1/2 teaspoon grated nutmeg
• superfine or confectioner’s sugar, for sprinkling

1. Preheat oven to 400°.
2. Combine the oil, water, vinegar, salt and sugar in a bowl.
3. Add flour until it becomes a dough, approx. 2 1/2 to 3 cups. (The finished dough should be thin, wet and look slightly mealy. The goal here is to get it to hold together and nothing more.)
4. Gently spread the dough onto greased baking paper in sheet pan, until it lies smooth, flat and thin.
5. Wash, halve and pit the plums. Lay them on the dough, cut side up, making neat rows. Bake the tart for 15 minutes.
6. Meanwhile, mix the heavy cream, eggs, vanilla extract, salt, sugar, and nutmeg together.
7. When the 15 minutes are up, carefully pour the custard mixture over the dough in the oven. Then bake the tart for 45-55 minutes or until golden-brown and slightly bubbling on top.
8. When finished, let cool, then cut into squares and sprinkle with superfine or confectioner’s sugar.