Mexican Lime Mousse Pie

Pour cold water into small metal bowl. Sprinkle gelatin over water and let stand until gelatin softens, about 10 minutes.

Whisk yogurt, sugar, lime juice and zest until creamy, in medium bowl.
Gently fold lime mixture into whipped cream.

Set bowl of gelatin in saucepan of barely simmering water; whisk until gelatin dissolves, about 1 minute. Whisk into creamy lime mixture.

Pour mixture into piecrust. Garnish with additional lime zest and lime slices.

Chill for at least 4 hours, up to overnight.