In the top of a double boiler, combine yolks, milk, 2/3 cup sugar, cornstarch and salt. Cook, stirring constantly, until mixture thickens. Stir in 1/2 teaspoon vanilla and 1 cup pecans. Pour filling into baked pie shell.
In a large glass or metal mixing bowl, beat egg whites until foamy. Beat in 1/2 teaspoon vanilla and gradually add 6 tablespoons white sugar, continuing to beat until stiff peaks form. Spread meringue over pie, covering completely. Sprinkle with 1/4 cup ground pecans.
Bake in the preheated oven for 10 to 15 minutes, or until meringue is delicately browned.
