Ginger Cardamom Oeufs à la Neige

Line bottom of a small 4-sided sheet pan with parchment paper.
Separate 2 eggs; put yolks in a large bowl and whites in another. Add whole egg to yolks.
Beat whites with a pinch of salt using an electric mixer until they hold soft peaks. Add 1/2 cup sugar in a slow stream, beating at medium-high speed until whites hold stiff, glossy peaks.
Meanwhile, bring milk to a bare simmer with ginger and cardamom in a wide 4-quart heavy pot over medium heat.
Drop 4 large dollops of beaten whites into milk and poach at a bare simmer, turning once, 4 minutes. Transfer with a slotted spoon to lined pan (reserve milk).
Whisk remaining 3 tablespoons sugar, cornstarch, and salt into yolk mixture. Add hot milk in a slow stream, whisking until incorporated, then return to pot. Cook, stirring often, until thickened and an instant-read thermometer registers 170°F. Strain through a fine-mesh sieve into a clean bowl. Stir in vanilla.
Quick-chill custard by setting bowl in an ice bath and stirring occasionally, about 20 minutes. Ladle into 4 bowls and put a meringue in each. Sprinkle with nuts.