How to Make It
Preheat to 325°F with rack in center of oven. Beat sugar and 6 tablespoons of the butter in a large bowl with an electric mixer on medium speed until fluffy, about 2 minutes. Add eggs and egg yolks, and beat until combined, about 1 minute. Add lime juice, and beat until combined, about 1 minute. (Mixture will look curdled.)
Pour mixture into a medium, nonreactive saucepan, and cook over low, stirring constantly, until smooth, about 2 minutes. Increase heat to medium, and cook, stirring constantly, until mixture coats the back of a spoon, 5 to 7 minutes. (Do not let mixture boil.) Pour mixture into a bowl, and place plastic wrap directly on warm curd (this will prevent a film from forming). Chill until completely cool, about 1 hour.
Stir together flour, powdered sugar, cornstarch, and salt in a large bowl. Add remaining 1 cup softened butter and beat with a hand-held electric mixer on low speed until coarse crumbs form, about 2 minutes. Increase speed to medium, and beat until smooth, about 1 minute more. Turn dough out onto floured surface. Form dough into a log, and wrap with plastic wrap; chill 30 minutes.
Divide dough into 12 equal portions. Roll each portion into a 4-inch round. Lightly coat a 12-cup muffin pan with non-stick spray. Fit 1 dough round into each cup, pressing into bottom and up sides; freeze 10 minutes.
Bake crusts in center of oven until golden brown, 20 to 25 minutes. (Prick bottom of crusts with a fork if they begin to puff.) Remove from oven, and cool completely, about 20 minutes. Gently remove pies from muffin pan. Spoon about 3 tablespoons of the cooled lime curd into each piecrust. Dollop with marshmallow crème, and top with toasted coconut.