For the crust: 5 cups all-purpose flour 6 tablespoons sugar 2 cup (4 sticks) unsalted butter, chilled and cut into small pieces 4 large egg yolks 1/2 cup ice water
For the creme fraiche filling: 2 packages cream cheese (8 ounces each), room temperature 1 teaspoon pure vanilla extract 8 ounces creme fraiche 1 cup confectioner's sugar
For the tart: 4 ounces semisweet chocolate 1/2 cup apricot jam, for glazing blueberries 1/2 cup raspberry jam, for glazing raspberries 2 tablespoons water 2 pints red raspberries Confectioners' sugar, for dusting 1 pint blueberries, picked over
To make the dough:
In the bowl of a food processor, combine flour and sugar. Add butter, and process until mixture resembles coarse meal, 10 to 20 seconds.
In a small bowl, lightly beat egg yolks; add ice water. With machine running, add the egg mixture in a slow, steady stream through the feed tube. Pulse until dough holds together without being wet or sticky; be careful not to process more than 30 seconds. To test, squeeze a small amount together: If it is crumbly, add more ice water, 1 tablespoon at a time.
Divide dough into two equal balls. Flatten each ball into a disk, and wrap in plastic. Transfer to the refrigerator, and chill at least 1 hour.
To make the filling: In the bowl of an electric mixer fitted with the paddle attachment, beat cream cheese and vanilla until soft. In a separate bowl, whisk creme fraiche with a balloon whisk until it holds soft peaks.
Whisk 1/3 of the creme fraiche into cream-cheese mixture to lighten. Fold in remaining creme fraiche while gradually sifting the confectioners' sugar over the top; fold just until combined.
To assemble the tart: On a lightly floured surface, roll out a disc of pate sucree 1/8 inch thick to fit a 3 3/4-by-13 1/4-inch fluted, rectangular tart pan with a removable bottom. Brush off excess flour with a dry pastry brush. Carefully transfer dough to tart pan, tuck dough into the edges, gently pressing along sides, and allow excess dough to overhang the edges. Trim the dough by running your rolling pin over the dough against the edges. Gently shape the edges by pressing the length of your forefinger against each flute along the sides. Prick all over the bottom with the tines of a fork. Repeat with remaining disc of dough. Transfer to the refrigerator, and chill for 1 hour.
Preheat oven to 375 degrees. Remove chilled tart shells from refrigerator, and line each with a piece of parchment paper that overhangs the edges by at least 2 inches. Fill parchment with pie weights or dried beans. Bake until just starting to color, about 20 minutes. Remove parchment and weights from tart shells, and return tart shells to oven. Continue baking until tart bottom is golden, about 20 minutes more. Transfer tart shells to a cooling rack, and allow to cool completely. Carefully remove tart shells from pan.
In a small bowl in the microwave or set over a pan of simmering water, heat chocolate until it is just melted, about 1 1/2 minutes; stir until smooth. Using the back of a spoon, line each tart shell with chocolate. Refrigerate to set, at least 5 minutes. Meanwhile, heat apricot and raspberry jams in two separate saucepans with about 1 tablespoon water in each; strain into separate small bowls.
Make top tart: Remove one lined tart shell from refrigerator and spread 1/3 of the creme fraiche filling over the bottom. Arrange 3 rows of unglazed raspberries 2/3 the length of the tart, leaving space between each row and at the top and bottom edges for 4 more rows. Dust with confectioners' sugar until raspberries are completely coated. Toss blueberries in a bowl with strained apricot jam. Fill left third of tart shell with a layer of glazed blueberries arranged snugly in rows; top with another layer of blueberries. Toss half the remaining raspberries with the strained raspberry jam, and carefully fill empty rows with some of the glazed raspberries, rinsing your hands as needed.
Make bottom tart: Remove remaining tart shell from refrigerator, and spread a third of the creme fraiche filling over the bottom. Arrange 3 rows of remaining unglazed raspberries, starting at the top edge and leaving space between each and at the bottom edge for 4 more rows. Dust with confectioners' sugar until raspberries are completely coated. Fill empty rows with remaining glazed raspberries.
Arrange tarts on a large board or tray to resemble the flag, and serve with remaining creme fraiche filling on the side. Finished tarts will hold at room temperature for several hours.