Prepare the Rich Tart Pastry; set aside.

Meanwhile, drain spinach in a colander, pressing with the back of a spoon to press out excess liquid; set aside. In a large skillet, cook onions in hot oil over medium heat for 5 minutes or until soft. Add drained spinach, oregano, salt, nutmeg, and pepper. Cook and stir until the spinach is heated through and any liquid has evaporated. Set aside to cool slightly.

In medium bowl, whisk eggs. Add goat cheese and milk, whisking until well combined. Stir in the cooled spinach mixture. Pour egg mixture into hot, baked pastry shell. Bake in a 325 degrees F oven for 35 to 40 minutes or until a knife inserted near center comes out clean. Let stand for 15 minutes before serving. Makes 8 to 10 servings.

In a medium bowl, stir together 1 cup all-purpose flour and 1/2 teaspoon salt. Using a pastry blender, cut in 1/3 cup butter until pieces are pea-size. Sprinkle 1 tablespoon of ice water over part of the flour mixture; gently toss with a fork. Push moistened dough to the side of the bowl. Repeat moistening flour mixture, using 1 tablespoon of water at a time, until all of the flour mixture is moistened, using 3 to 4 tablespoons water total. Form dough into a ball. Flatten the ball to a 1-inch-thick disk. Wrap dough with plastic wrap and refrigerate for 30 to 60 minutes. On a floured surface, roll dough from center to edges in to a circle about 12 inches in diameter. To transfer pastry, wrap it around the rolling pin. Unroll pastry into a 11-inch tart pan with a removable bottom. Ease pastry into pan without stretching it. Press pastry into fluted sides of tart pan and trim edges. Do not prick pastry. Line pastry with a double thickness of foil. Bake in a 450 degree F oven for 8 minutes. Remove foil. Bake 4 to 5 minutes more or until lightly browned. Cool slightly on a wire rack.

If desired, line a 9-inch pie plate with pastry. Bake pastry as directed above. Cool slightly on a wire rack. Spoon filling in partially baked pie crust. Bake in a 325 degree F oven for 45 minutes or until a knife inserted near the center comes out clean.