Prepare lemon grass stalks by peeling off the outer husk and placing on a solid cutting board. Bruise the stalks with the back of a thick knife. Wrap each stalk in a piece of cheesecloth and tie with strings.
In a stainless steel saucepan combine the water and sugar and bring to a boil, stirring once to make sure sugar has dissolved. Add one prepared lemon grass stalk and remove from heat. Allow lemon grass to steep in syrup until cooled.
In a stainless steel saucepan combine heavy cream and the second prepared lemon grass stalk. Bring cream to a boil, remove pan from heat and allow to cool.
Remove lemon grass stalks from cream and sugar syrup.
Place yogurt in a large stainless steel bowl. Whisk in the cool lemon grass-infused cream and lemon grass syrup. Keep mixture chilled until ready to serve.
Just before serving add lime juice to yogurt mixture. Adding lime juice too early will cause soup to curdle.
Ladle soup into chilled bowls or flat soup plates. Place a scoop of lime granita (or sherbet) in the center of the bowl and garnish with lime zest. Additional accompaniments include gingersnap cookies and/or thinly sliced tropical fruits such as papaya or kiwi.
Recipe courtesy of Stan Frankenthaler, Executive Chef/Owner of Salamander Restaurant, Cambridge, MA