Make the dough:
In a food processor, grind the walnuts w ith the sugar to a sandy texture. Add the flour, cinnamon, lemon zest, salt, cloves, and crumbled hard-cooked egg yolks. Pulse briefly to combine. Add the butter and pulse until the dough starts to come together and looks clumpy. Add the raw yolks and vanilla and pulse until well combined. The dough will be sticky and moist, more like a cookie dough than a pastry dough. Cut the dough in half (each piece should be about 12-3/4 ounces), set each half on a large piece of plastic, and shape each into a flat disk, using the plastic to help you flatten. Wrap each disk in its plastic and refrigerate for at least 1 hour.
Assemble the tart:
On a floured work surface, roll each disk of dough into an 11-inch round about 1/4 inch thick. Put one round on a plate and refrigerate, uncovered. Fit the other round into a 9-inch fluted tart pan with a removable bottom. Fold the excess dough into the sides of the pan and press to get an edge flush with the top of the pan, about 1/3 inch thick. Sprinkle 2 Tbs. of the flour on the bottom of the tart and spread to evenly cover. Toss the pears and cranberries with the remaining 1/4 cup flour. Arrange the fruit in the tart shell so that the pears lie as flat as possible and there are some berries showing on top. Scrape any remaining flour over the fruit and sprinkle with the sugar.
Take the other piece of dough from the refrigerator and cut it into eight 1-inch-wide strips. (I use a ruler and a ravioli cutter or a pastry cutter to get beautiful zigzag-edged strips). Arrange four strips, evenly spaced, over the top of the tart. Then, on a sharp diagonal to the first four, set the other four strips on top, so that the overlapping layers make diamond shaped windows. Trim the ends of the strips and press them into the edges of the tart.
Bake the tart:
Position an oven rack on the bottom rung. Line a heavy rimmed baking sheet with foil and set it on the rack. Heat the oven to 350°F. Whisk the egg yolk with the cream or milk. Brush the tart's lattice top with the egg glaze. Bake on the baking sheet until the pastry is golden brown, 45 min. to 1-1/4 hours. Let cool on a rack for 1 hour and serve slightly warm.
Make Ahead Tips
This recipe was developed to be made ahead and frozen for up to six weeks. Immedieately wrap the assembled, unbaked tart tightly in plastic. (If you're freezing for longer than 1 week, add an outer layer of foil as well.) Store in coldest part of the freezer (generally the top). When ready to bake, position an oven rack on the bottom rung. Line a heavy rimmed baking sheet with foil and set it on the rack. Heat the oven to 350°F. Remove the tart from the freezer, unwrap, and glaze the frozen tart's lattice top with the egg wash (do not thaw the tart). Bake as directed above, until golden brown (baking time will be 1-1/4 to 1-1/2 hours).
Photo: Scott Phillips