PreparationMake the puff pastry: In a large bowl, sift together the flour and salt. Using a knife, stir in about 1 cup of water. Continue stirring until the dough just starts to come together but is still stringy and clumped together. Stir in more water as needed (you will probably use about 1 3/4 cups total), until the dough is smooth and gathers itself into a ball-like shape. Turn the dough out onto a lightly floured surface, and using a rolling pin, roll it into a long, 1/2-inch-thick rectangle. Arrange all of the butter in the center of the dough, 2 sticks on top of 2 sticks, so that the butter divides the rectangle of dough in half. Fold one long end of the dough over the butter, and then fold the other long end on top, like folding a business letter. Wrap the dough in plastic wrap and refrigerate for 10 minutes. Return the dough to the lightly floured surface and roll into a long, 1/2-inch-thick rectangle. Fold one long end of the dough toward the center, then fold the other long end on top. Wrap the dough in plastic wrap and refrigerate for 10 minutes. Repeat this step 1 more time so that the dough has been rolled, folded, and refrigerated a total of 3 times. DO AHEAD: The puff pastry can be prepared in advance and refrigerated, wrapped in a double layer of plastic wrap, up to 3 days. It can also be frozen for up to 3 months. Position a rack in the middle of the oven and preheat to 325°F. Butter an 8-inch deep-dish pie plate. On a lightly floured surface, roll the puff pastry into a 1/4-inch-thick circle about 12 inches in diameter. Fit the dough into the prepared pie plate, remove any excess dough, and reserve the excess for another use. If desired, use a fork to crimp the edge of the tart. Using a fork, prick the bottom and sides of the tart shell all over, then chill 15 minutes. Line the tart shell with parchment paper and fill with pie weights or dried beans, then bake until the pastry is set and pale golden along the edge, about 15 minutes. Remove the weights or beans and the parchment paper, then gently brush the bottom and sides of the tart shell with the egg white and cook for an additional 5 minutes. Remove the tart from the oven and spread the jam evenly across the bottom. Set aside to cool. Make the filling: In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugar and beat until light and fluffy and pale in color, about 2 minutes. Add the eggs, 1 at a time, beating well after each addition and scraping down the bowl as necessary, about 2 minutes total. Using a spatula, gently fold in the flour. Pour the batter onto the jam in the cooled tart shell and smooth the top. Bake until the tart is golden and set, 40 to 45 minutes. Transfer tart to rack to cool and serve warm or at room temperature.
PreparationMake the puff pastry: In a large bowl, sift together the flour and salt. Using a knife, stir in about 1 cup of water. Continue stirring until the dough just starts to come together but is still stringy and clumped together. Stir in more water as needed (you will probably use about 1 3/4 cups total), until the dough is smooth and gathers itself into a ball-like shape. Turn the dough out onto a lightly floured surface, and using a rolling pin, roll it into a long, 1/2-inch-thick rectangle. Arrange all of the butter in the center of the dough, 2 sticks on top of 2 sticks, so that the butter divides the rectangle of dough in half. Fold one long end of the dough over the butter, and then fold the other long end on top, like folding a business letter. Wrap the dough in plastic wrap and refrigerate for 10 minutes. Return the dough to the lightly floured surface and roll into a long, 1/2-inch-thick rectangle. Fold one long end of the dough toward the center, then fold the other long end on top. Wrap the dough in plastic wrap and refrigerate for 10 minutes. Repeat this step 1 more time so that the dough has been rolled, folded, and refrigerated a total of 3 times. DO AHEAD: The puff pastry can be prepared in advance and refrigerated, wrapped in a double layer of plastic wrap, up to 3 days. It can also be frozen for up to 3 months. Position a rack in the middle of the oven and preheat to 325°F. Butter an 8-inch deep-dish pie plate. On a lightly floured surface, roll the puff pastry into a 1/4-inch-thick circle about 12 inches in diameter. Fit the dough into the prepared pie plate, remove any excess dough, and reserve the excess for another use. If desired, use a fork to crimp the edge of the tart. Using a fork, prick the bottom and sides of the tart shell all over, then chill 15 minutes. Line the tart shell with parchment paper and fill with pie weights or dried beans, then bake until the pastry is set and pale golden along the edge, about 15 minutes. Remove the weights or beans and the parchment paper, then gently brush the bottom and sides of the tart shell with the egg white and cook for an additional 5 minutes. Remove the tart from the oven and spread the jam evenly across the bottom. Set aside to cool. Make the filling: In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and sugar and beat until light and fluffy and pale in color, about 2 minutes. Add the eggs, 1 at a time, beating well after each addition and scraping down the bowl as necessary, about 2 minutes total. Using a spatula, gently fold in the flour. Pour the batter onto the jam in the cooled tart shell and smooth the top. Bake until the tart is golden and set, 40 to 45 minutes. Transfer tart to rack to cool and serve warm or at room temperature.