Preparation

1. 1. On a lightly floured surface, roll out the pastry into an 11-inch circle that is about ¹/8 inch thick.
2. Reverse the dough onto the rolling pin and unroll it evenly over a 9-inch tart pan. Press the dough lightly into the pan, lifting the edges and working it gently down into the bottom edge of the pan.
3. Trim off excess dough by rolling the pin over the top of the pan. With your thumbs, push the dough ¹/8 inch above the edge of the mold, to make an even, rounded rim of dough around the inside circumference of the pan. Chill in refrigerator for about 30 minutes.
4. 2. Preheat oven to 400°F with the rack in the middle position. Using the tines of a fork, prick the dough evenly all over, but make sure not to go entirely through the dough. Line the shell with parchment and weigh it down with pie weights, dried beans, or rice. Put the tart shell in the oven and bake until the dough under the parchment is no longer wet, about 20 minutes. Remove the beans/rice and parchment and continue baking for another 2 minutes, until the shell is lightly brown. Brush with egg white immediately. Reserve.
5. 3. While the tart shell is baking, prepare the filling. Insert the chopping blade into the work bowl of the food processor. With the machine running on High, drop the garlic through the feed tube to finely chop. Keeping the garlic in the work bowl, remove the chopping blade (set aside – it will be used again) and insert the slicing disc at setting 4. Roll the kale leaves together and slice. Then slice the mushrooms, at the same setting.
6. 4. Put the oil into a medium skillet (about 10 inches) set over medium-low heat. Once oil is hot, add the garlic with a pinch of the salt and the pepper. Sauté until softened and fragrant, but has picked up no color. Add the sliced kale and mushrooms, remaining salt, and the thyme. Sauté until the kale is bright and wilted and the mushrooms are starting to brown and softened. Remove and reserve.
7. 5. Remove the slicing disc and replace with the fine shredding disc. Shred the Gruyère on Low. Remove and reserve.
8. 6. Remove the shredding disc and replace with the chopping blade. Process the milk, cream, and eggs on Low until combined, about 20 seconds. Reserve custard in bowl.
9. 7. Spread the kale/mushroom mixture in the tart shell, pour in custard and sprinkle cheese on top.
10. (Depending on your tart/pie pan, all of the custard may or may not fit. Do not overfill.)
11. 8. Carefully place the quiche in the preheated oven. Bake until just set, about 20 minutes.
12. 9. Allow to cool for about 5 minutes before slicing and serving.