SHERRY THORUP. . . SWEET POTATO PIE

 
 

1 1/2 cup fresh (cooked) or canned sweet potatoes or yams 1/2 cup sugar 1 teaspoon cinnamon 1 teaspoon allspice 1/2 teaspoon salt 2 eggs, beaten 1 cup evaporated milk 2 Tablespoons butter, very soft 1 9-inch unbaked