Position a rack incenter of oven; preheat to 250°F. Line abaking sheet with parchment paper. Usingan electric mixer, beat egg whites and creamof tartar in a large bowl until soft peaks form.Beat in vanilla. Gradually beat in cornstarch,then sugar, 1 tablespoon at a time; continue tobeat until stiff peaks form. Fold in pistachios.
Spread meringue on parchment paper ina 1/3" layer (meringue will not completelycover parchment).
Bake meringue until crisp,about 55 minutes.
Let cool, then break intosmall pieces. DO AHEAD: Can be made 1 dayahead. Store airtight.
Combine sugar,ginger, and 1/4 cup water in a small saucepan.Scrape in seeds from vanilla bean; add bean.Bring to a boil over medium heat, stirringuntil sugar dissolves.
Remove saucepanfrom heat and let infuse for 30 minutes.Discard bean. Cover and chill ginger syrup.
In a small bowl, whisk together yogurt,cream, and ginger syrup just to blend.
Place mixture in a whipped-cream canister.DO AHEAD: Can be made 4 hours ahead.Chill. Dispense into bowls according tomanufacturer’s instructions. (Alternatively,double ingredients and whip chilled creamuntil stiff peaks form, then whip in yogurtand syrup. Spoon the mixture into bowls.)Top with crumbled pistachio meringue.
