How to Make It
In a food processor, pulse the flour with the sugar and salt. Add the butter and pulse until the mixture resembles coarse meal with some pea-size pieces of butter remaining. With the machine on, slowly drizzle in the cream, then the ice water, until the dough just holds together. Turn the dough out onto a lightly floured surface and knead 3 times, until it just comes together. Pat the dough into a 1-inch-thick disk. Wrap in plastic and refrigerate for at least 1 hour or overnight.
Preheat the oven to 375°. Line a work surface with a 12-by-14-inch sheet of parchment paper. Roll out the dough on the paper into a 12-inch round, about 1/8 inch thick. Transfer the paper and dough to a baking sheet and refrigerate until the dough is firm but still pliable, about 15 minutes.
In a large bowl, toss the pears with 4 tablespoons of the sugar. In a small bowl, whisk the egg, cream and vanilla.
Brush the dough with the egg wash, leaving a 2-inch border all around. Spread the pear mixture over the dough, leaving a 2-inch border, and sprinkle the chocolate, hazelnuts, salt and 2 tablespoons of the sugar on top. Fold the edge of the dough up and over the pears, pinching the folds. Brush the folded edge with egg wash and sprinkle with the remaining 1 tablespoon of sugar.
Bake the galette for about 1 hour and 15 minutes, until the crust is golden brown. Slide a large spatula under the galette to release it from the parchment paper, then let cool to room temperature on the baking sheet. Transfer the galette to a platter and serve with
ice cream or whipped cream.