In a separate bowl, combine flour, salt, baking soda and sugar. Add to wet ingredients one third at a time, mixing until batter is smooth. Then fold in butter.
Heat oil to 350F. Pour batter into a funnel and close the opening with your finger or funnel stopper. Release the batter from the funnel and pour batter in a line (it will look like ribbons) and stop flow. Fry 3 to 4 at a time, until golden brown on all sides.
Remove fries, drain, and sprinkle with powdered sugar. Serve immediately.