Have ready eight 4-inch metal pie pans, and prepare an ice-water bath.
In a small saucepan, combine 2 cups sugar and 1 cup water; set over medium-high heat. Cook, stirring, until sugar has dissolved. Cover, and bring to boil; cook until condensation washes down sides. Remove cover; boil until syrup turns deep amber in color. Quickly submerge pan in ice-water bath.
Working quickly, divide caramel among the pie pans; swirl each to coat bottom. Set aside to cool.
Heat oven to 325 degrees. Pour milk into a saucepan, and set over high heat. Bring just to a boil; set aside.
In a large bowl, combine pumpkin puree, remaining 3/4 cup sugar, ginger, nutmeg, cinnamon, salt, whole eggs, and egg yolks. Mix in vanilla and warm milk; pass through fine sieve, discarding solids. Divide mixture among pie pans, filling two-thirds full. Transfer pie pans to a roasting pan.
Loosely drape piece of foil over top of roasting pan, transfer to oven, and add enough boiling water to the roasting pan to come halfway up sides of pie pans (always fill roasting pan with boiling water after transferring to oven, to avoid burning). Bake until centers are nearly set -- a thin-bladed knife inserted into centers should come out clean -- 60 to 65 minutes. Transfer roasting pan to wire rack to cool. Remove flans from water, and dry bottoms of pie pans. Cover with plastic wrap, and refrigerate flans overnight.
Heat oven to 375 degrees. Have ready four 5-inch flan rings or fluted tartlet tins; line two baking sheets with parchment. On a lightly floured surface, roll out pate brisee to an 1/8-inch thickness. Cut out eight 7-inch circles. Ease a circle into each flan ring, letting excess drape over top. Fit dough into bottom corners of rings, using knuckles to work dough from top down, not from the center out. Using a rolling pin, roll over tops of rings, creating neat tops and removing any excess dough. Prick bottom of each shell several times with a fork. Transfer shells to baking sheets, and chill 30 minutes.
Line shells with foil, and fill with pie weights or dried beans. Bake 20 minutes, and remove foil and weights. Bake until shells are golden brown, 2 to 4 minutes more. Transfer baking sheets to a wire rack, and let shells cool, 1 hour. Remove shells from rings.
When ready to serve, place shells on four dessert plates. Unmold flan by running a knife carefully around edge of pan, and invert it over a shell; caramel sauce will flow, filling shell. Repeat with remaining shells and flan. Top with whipped cream or creme fraiche, if desired.