Preparation Position 1 rack in bottom third and 1 rack in top third of oven; preheat to 200°F. Line 2 large baking sheets with parchment paper. Using 3 1/4- to 3 1/2-inch-diameter cookie cutter as template, heavily trace 4 circles on each parchment sheet. Turn parchment over so that marked side faces down (circles will show through). Whisk sugar and cornstarch in medium bowl to blend. Using heavy-duty or handheld electric mixer on medium-high speed, beat whites in large bowl until foamy, about 1 minute. Add cream of tartar; beat until soft peaks form, about 1 minute. Add sugar mixture, 1 tablespoon at a time, beating until whites are very stiff and glossy, at least 4 minutes with heavy-duty mixer and 6 to 8 minutes with handheld. Scoop enough meringue into pastry bag fitted with medium star tip to fill 1/3 full. Pipe small dot of meringue under parchment in each corner of baking sheets. Press parchment onto dots. Starting in center of 1 marked circle, pipe meringue in continuous spiral to fill circle completely. Pipe 1 meringue circle atop edge of base circle, forming standing rim. Repeat, piping 2 more circles atop first, forming meringue cup. Pipe 3 more cups on sheet, filling bag with meringue as needed. Pipe 4 cups on second sheet. Bake meringues 3 hours without opening oven door (sides of meringues may settle slightly). Turn off oven; let meringues stand in closed oven over-night to dry completely. (Can be made 1 week ahead. Store airtight in single layer.) Whisk jam, sugar and 1/3 cup water in heavy medium saucepan over medium-high heat until sugar dissolves and jam melts. Boil until sauce thickens and is reduced to generous 3/4 cup, whisking often, about 7 minutes. Add berries and cardamom; stir gently. Remove from heat; let stand 1 hour to thaw fruit. Cover; chill at least 2 hours and up to 1 day. Scoop sorbet into vacherins. (Can be made 2 days ahead. Wrap tightly; freeze. If you freeze the vacherins, the meringues will be tender and chewy rather than crisp.) Spoon sauce over. Garnish with berries and mint. Serve with remaining sauce.
Preparation Position 1 rack in bottom third and 1 rack in top third of oven; preheat to 200°F. Line 2 large baking sheets with parchment paper. Using 3 1/4- to 3 1/2-inch-diameter cookie cutter as template, heavily trace 4 circles on each parchment sheet. Turn parchment over so that marked side faces down (circles will show through). Whisk sugar and cornstarch in medium bowl to blend. Using heavy-duty or handheld electric mixer on medium-high speed, beat whites in large bowl until foamy, about 1 minute. Add cream of tartar; beat until soft peaks form, about 1 minute. Add sugar mixture, 1 tablespoon at a time, beating until whites are very stiff and glossy, at least 4 minutes with heavy-duty mixer and 6 to 8 minutes with handheld. Scoop enough meringue into pastry bag fitted with medium star tip to fill 1/3 full. Pipe small dot of meringue under parchment in each corner of baking sheets. Press parchment onto dots. Starting in center of 1 marked circle, pipe meringue in continuous spiral to fill circle completely. Pipe 1 meringue circle atop edge of base circle, forming standing rim. Repeat, piping 2 more circles atop first, forming meringue cup. Pipe 3 more cups on sheet, filling bag with meringue as needed. Pipe 4 cups on second sheet. Bake meringues 3 hours without opening oven door (sides of meringues may settle slightly). Turn off oven; let meringues stand in closed oven over-night to dry completely. (Can be made 1 week ahead. Store airtight in single layer.) Whisk jam, sugar and 1/3 cup water in heavy medium saucepan over medium-high heat until sugar dissolves and jam melts. Boil until sauce thickens and is reduced to generous 3/4 cup, whisking often, about 7 minutes. Add berries and cardamom; stir gently. Remove from heat; let stand 1 hour to thaw fruit. Cover; chill at least 2 hours and up to 1 day. Scoop sorbet into vacherins. (Can be made 2 days ahead. Wrap tightly; freeze. If you freeze the vacherins, the meringues will be tender and chewy rather than crisp.) Spoon sauce over. Garnish with berries and mint. Serve with remaining sauce.