Brown-Sugar Buttermilk Pie

Ingredients

• 3 to 5 tablespoons ice water
• 1 cup packed dark-brown sugar
• 3 large eggs plus 2 large egg yolks, lightly beaten
• 1/4 teaspoon fine salt
• 1 1/2 cups buttermilk, room temperature
• 1/2 cup (1 stick) cold unsalted butter, cut into small pieces
• 6 tablespoons (3/4 stick) unsalted butter
• 1/2 teaspoon ground nutmeg
• 1 teaspoon sugar
• 3 tablespoons all-purpose flour
• 1/4 teaspoon ground cinnamon
• 1 1/4 cups all-purpose flour, spooned and leveled, plus more for rolling