Granny’s Cocoa Cream Pie

Name: Granny’s Cocoa Cream Pie
Ingredients: 1/2 c. cocoa; 1/4 cup cornstarch/or arrowroot powder (or 1/2 c. all purpose flour); 3 egg yolks; 1 1/2 c. sugar; 1/4 tsp. salt; 2 c. milk; 1 tsp. vanilla; 9 " pre-baked pie shell