This tart is a little more elegant than a standard quiche, and intended to be baked in a 9- or 10-inch flan ring or loose bottom fluted pan – the kind where you can detach the bottom from the sides after baking. But if you don’t have either of those pieces of kitchen equipment, you can bake the tart in a regular pie pan. A shallow, metal, 9-10 inch pie pan will work best. The custard is made with heavy cream, so it’s rich, but there’s no cheese in the tart.
Crust:
1 cup all-purpose flour
a pinch or two of kosher salt
6 tablespoons cold unsalted butter, cut into bits
1 large egg, lightly beaten
a few tablespoons of water if necessary
Filling
half a large onion, finely chopped – about 3/4 cup
1 pound of medium asparagus, washed trimmed
1 tablespoon butter
Kosher salt & freshly ground black pepper, to taste
1 cup heavy cream
3 large eggs, one separated
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- Make the crust: combine the flour and salt in a bowl , food processor, ir bowl of a stand mixer. Slice in the butter, and mix with your fingertips or a pastry blender, or pulsing in the food processor, or with the paddle attachment of the mixer until most of mixture resembles coarse meal with only a few butter lumps. Drizzle the egg in and mix just until the dough starts to come together, adding water by the tablespoon if needed.
- In the bowl or on a floured surface, gather the dough into a ball, and flatten into a disk. Wrap airtight in plastic wrap or other reusable wrapping and chill for at least 30 minutes and up to 2 days.
- Make filling: bring several inches of water to a boil in a wide deep skillet, add salt, and then add the asparagus spears. Cook just until the asparagus is bright green, then with tongs transfer to a colander set in the sink, and run cold water over to stop the cooking. Drain the asparagus well.
- Empty the skillet and dry it, then melt the butter and sautée the onion gently until tender but not browned. Meanwhile cut the tips off the asparagus in about 3-inch lengths and slice the remaining stalks into 1-inch pieces. Reserve the tips. When the onion is soft add the sliced asparagus, season with salt and pepper, mix well, and remove from the heat.
- Assemble the tart: heat the oven to 375°. Roll out the crust and fit it into the pan of your choosing. If using a flan ring or fluted tart pan place it on a cookie sheet or pizza pan lined with parchment to catch any drips. Trim the overhang, leaving enough to build up a double thickness for a nice sidewall. If using a pie dish crimp the edges, and optionally set it on a cookie sheet or pizza pan to catch any drips.
- Brush the crust all over with the white of the separated egg. Beat the yolk and the remaining eggs together and add the cream. Spoon the onion and sliced asparagus stalks into the crust and pour the custard over.
- Bake the tart for about 20 minutes until the filling is starting to set but there are still liquid spots. Remove from the oven and scatter the asparagus tips over the top of the tart, pressing down gently to settle them in the custard. Return the tart to the oven and bake another 20-30 minutes until fully set.
- Cool tart on the baking sheet on a rack for 15-30 minutes, then if using a flan ring or tart pan, loosen edges with a small sharp knife, and lift off the sides for easier cutting. Serve warm or at room temperature.