Cream butter and shortening; gradually add brown sugar, beating until light and fluffy. Add eggs, beating well. Combine flour, salt and baking soda; add to creamed mixture, beating well. Stir in pecans. Drop dough by level tablespoonfuls 2 inches apart onto lightly greased cookie sheets. Bake at 350 degrees for 12 to 15 minutes. Cool slightly on cookie sheets; remove to wire racks. Makes 5 dozen.