"My great grandma's recipe... these cookies have been at all our holiday family gatherings since the 1940s" -Tami Bowman
Stir together flour, soda and salt. Beat butter at medium speed with an electric mixer until creamy; gradually add flour mixture, mixing well. Stir in vanilla. (Dough will be soft.) Cover and chill 30 minutes. Arrange pecan halves in groups of five on greased baking sheets to resemble head and legs of turtle.
Shape dough into 1 1/2-inch balls, using a rounded teaspoonful of dough for each so tips of nuts will show when cookies are baked. Dip bottom of dough into unbeaten egg white and press lightly onto nuts; flatten tops slightly.
Bake at 350° for 12 to 14 minutes. (Do not overbake.) Cool completely on wire racks.
Beat butter in a small mixing bowl at medium speed with an electric mixer until creamy. Gradually add sugar, cocoa, and whipping cream, beating until smooth. Generously spread frosting on top of cookies.