Beat butter, sweet potato, white sugar, brown sugar, and orange juice with an electric mixer in a large bowl until smooth.
Add eggs whites one at a time, allowing each egg to blend into butter mixture before adding the next. Beat in vanilla extract. Dissolve baking soda in hot water in a small bowl.
Add to sweet potato batter. Stir in flour, chocolate chips, and walnuts.
Roll dough into walnut-sized balls and place 2 inches apart onto ungreased baking sheets.
Bake in preheated oven until edges are nicely browned, about 10 minutes.