1. Preheat oven to 325°. Mix graham cracker crumbs, 1/4 cup macadamia nuts, granulated sugar, and butter with hands; press firmly into a 10-inch pie plate. Bake at 325° for 15 minutes or until lightly browned. Remove and let stand 15 minutes.
2. Whisk together condensed milk, lime juice, and eggs until well blended. Pour into crust, and bake at 325° for 18 to 20 minutes or until set. Chill at least 4 hours.
3. Combine crème fraîche and powdered sugar. Spread evenly over pie, and garnish, if desired.