- 1½ pounds sweet potatoes, peeled and cut into ½-inch cubes
- 1 onion, chopped
- ½ teaspoon ground turmeric
- ½ teaspoon garam masala
- 3 tablespoons olive oil
- Salt and freshly ground pepper
- Pastry dough
- 6 slices cooked bacon, chopped
- ¼ cup fresh parsley, chopped
- 8 ounces Gruyère cheese, shredded
- 1½ cups half-and-half
- 4 large eggs
- 1 teaspoon minced fresh rosemary, plus sprigs for garnish
- 1¼ cups all purpose flour
- ¼ teaspoon fine salt
- 8 tablespoons cold butter, cut into pieces
- 1 egg yolk
- 3 tablespoons cold water
In a food processor, combine flour and salt. Pulse in butter until incorporated and mixture resembles clumpy wet sand. Add egg and water and process until a dough forms. Pat dough into a disk, wrap and refrigerate until ready to use.
Heat oven to 425°. Combine potatoes, onion, turmeric, masala, olive oil and salt and pepper to taste on a large rimmed baking sheet. Roast until tender and beginning to brown, about 20 minutes, tossing occasionally. Let cool while preparing the pastry. On a lightly floured work surface, roll dough into a 13-inch circle. Transfer dough to an 11-inch tart pan and press to fit. Use a fork to prick holes all around the bottom of the crust and up the sides. Line with parchment, fill with dried beans or pie weights and place on a baking sheet. Bake until golden, about 17 minutes. Reduce oven to 350°.
Combine potato mixture with bacon and parsley. With tart still on baking sheet, layer half of potato mixture into crust, top with cheese and then remaining potatoes.
Whisk together half-and-half, eggs and rosemary. Season with salt and pepper and pour over potatoes. Bake on lowest oven rack until set, about 35 minutes. Let rest 15 minutes before serving.