Ingredients

PASTRY

1. 2 cups all-purpose flour
2. 1/2 cup hazelnuts, toasted (see Note) and chopped
3. 1 tablespoon cinnamon
4. 1/2 teaspoon cloves
5. 1/2 teaspoon allspice
6. 2 sticks ( 1/2 pound) unsalted butter, diced and chilled
7. 2 hard-cooked egg yolks, pressed through a strainer
8. 1 1/2 tablespoons finely grated lemon zest
9. 1/4 cup ice water

FILLING

1. 3/4 cup sugar
2. 1/2 cup hazelnuts, toasted (see Note) and chopped
3. 2 tablespoons finely grated fresh ginger
4. 5 Bosc pears--peeled, cored and cut into 1-inch dice
5. 3 tablespoons all-purpose flour

THYME CREAM

1. 1 cup heavy cream
2. 1/2 cup confectioners' sugar
3. 1 1/2 teaspoons chopped thyme

Directions

1. Make the pastry: In a food processor, combine the flour, hazelnuts, cinnamon, cloves, and allspice and process until the nuts are finely ground. Add the butter, egg yolks and lemon zest and pulse until the mixture resembles coarse meal. Add the ice water and pulse just until the dough comes together. Scrape the dough onto a lightly floured work surface and knead briefly. Pat the dough into a disk, wrap in plastic and refrigerate until firm, about 1 hour.
2. Preheat the oven to 350°. Cut off a third of the dough and keep it refrigerated. On a lightly floured surface, roll out the remaining dough to a 13-inch round. Fold the dough in half and transfer it to an 11 1/2 -inch tart pan with a removable bottom. Unfold the dough and press it into the pan and up the side as evenly as possible. Refrigerate the shell. 
3. On a lightly floured surface, roll out the remaining piece of dough to a 13-by-8-inch rectangle. Place the rectangle on a baking sheet and freeze until very firm. Using a pizza cutter or a sharp knife, cut the rectangle lengthwise into 10 strips, cutting directly on the pan. Refreeze the strips until needed. 
4. Make the filling: In a food processor, combine 1/4 cup of the sugar with the hazelnuts and ginger and process to a coarse powder. In a large bowl, toss the pears with the remaining 1/2 cup of sugar and the flour. Remove the tart shell from the refrigerator. Spread the hazelnut and ginger mixture over the bottom of the shell and top with the pears. Arrange the frozen dough strips over the filling in a lattice pattern. 
5. Bake the tart in the center of the oven for about 1 1/2 hours, or until the pastry is brown and the filling is bubbling. Let cool on a rack for at least 10 minutes. 
6. Make the thyme cream: Meanwhile, in a large bowl, whip the cream until soft peaks form. Add the confectioners' sugar and thyme and beat until firm; do not overbeat. Serve the tart warm, with the thyme whipped cream. 
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Make Ahead

The tart shell and lattice top can be frozen for up to 1 week.

Notes

Spread the hazelnuts in a pie plate and toast in a 400° oven for about 8 minutes, or until fragrant and browned. Let cool, then rub the nuts together in a kitchen towel to remove the skins.