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1
Preheat the oven to 375F.
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2
Have ready a 4 1/2 x 14-inch bottomless rectangular tart form or one with a removable bottom on a parchment-lined baking sheet.
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3
On a lightly floured surface, roll the dough into a 7 x 16-inch rectangle.
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4
Fit the dough into the mold, and trim the sides flush with the top of the mold.
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5
Transfer the shell to the freezer to chill for 20 minutes.
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6
Remove the shell from the freezer, prick the bottom with a fork, and line with parchment paper cut to fit.
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7
Fill with dried beans or metal pie weights.
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8
Bake until the crust is just beginning to brown, about 15 minutes.
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9
Remove from the oven, and remove the beans or weights.
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10
Return the crust to the oven, and bake until golden brown, about 10 minutes more.
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11
Remove from the oven, and set aside on a wire rack.
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12
Using a mandoline or vegetable peeler, very thinly slice 1 green zucchini and 1 yellow squash lengthwise.
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13
Place the slices in a colander in a single layer, and sprinkle lightly with salt.
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14
Place the colander in a bowl; let drain for 30 minutes.
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15
Cut the remaining zucchini and squash into 1/3-inch dice.
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16
Melt the butter in a large skillet over high heat.
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17
Add the leeks and squash, and season with salt and pepper.
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18
Cook until golden brown but still firm, about 8 minutes.
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19
Evenly distribute the cooked vegetables in the crust.
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20
Sprinkle the Gruyere on top.
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21
Place the salted squash slices in between double layers of paper towels.
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22
Gently press down to remove as much liquid as possible.
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23
Alternating squash colors, weave a lattice pattern over the top of the cheese and vegetables, covering the entire surface.
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24
Trim or tuck in the ends to fit.
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25
In a medium bowl, whisk together the egg, egg yolk, and cream, and season with salt and pepper.
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26
Lift the edges of the lattice in several places, and pour in the egg mixture.
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27
Using a pastry brush, coat the lattice with olive oil.
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28
Bake, loosely covered with aluminum foil, until the custard is set, 30 to 35 minutes.
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29
Remove the lattice tart from the oven, and place on a wire rack to cool slightly before serving.